1
Q
For every sense there is a….
A
Sensory receptor organ
2
Q
Define sensation
A
The registration of events from the environment on the sensory receptors.
3
Q
Define perception
A
The subjective interpretation of sensations by the brain
4
Q
What do sensory receptor organs do to environmental stimuli? What does this result in?
A
Filter environmental stimuli
- Detect and respond to some events, not others (prevents us from getting overwhelmed)
5
Q
What do sensory receptor organs transduce?
A
They transduce physical signals to neural code
6
Q
True or false: every species has a distinct window on the world
- Explain
A
True; they are sensitive to different stimuli, and have unique CNS to interpret these stimuli
7
Q
What is a sensory modality?
A
Each type of sensory neuron can respond to one type of sensation (e.g. touch, pain, vision, hearing)
8
Q
What two classes are sensory modalities grouped into?
- Briefly describe each
A
- General senses: receptors throughout the body
- Special senses: Receptors located in sense organs, such as eye, ear, etc.
9
Q
What are the 5 general senses?
A
- Somatic
- Tactile
- Thermal
- Pain
- Proprioreceptive
10
Q
What are the 5 special senses?
A
- Smell
- Taste
- Vision
- Hearing
- Balance
11
Q
What is the special adaptation that we discussed with regards to sharks? What other animal also shows this adaptation?
A
Sharks have electrical field detectors (Ampullae of Lorenzini, jelly-filled canals)
- Detect the itty-bitty electrical charges a fish makes when it flexes its muscles (recall that ion flow causes muscle contractions)
- Platypus can also do this
12
Q
Explain how some species sense magnetic fields, and provide 4 examples of organisms that do this
A
The earth’s magnetic fields provide orientation cues
- Species contain magnetite in their brains (mineral that is sensitive to magnetic fields)
- Fish, birds, butterflies and bats orient and migrate
13
Q
How many types of signals can a neuron send? What is the signal?
A
One; action potential
14
Q
What is the labelled lines hypothesis?
A
Hypothesis for describing how the brain knows what type of sensory stimulus it has received.
- Each and every sense has its own pathway (correct to some extent, but often too simple of an explanation)
15
Q
True or false: for each sense, there is an unlimited range of intensities to which we are sensitive
A
False; there is a limited range for each sense
16
Q
What does the range of sensory detection depend on? What are some examples of this range?
A
Differs between species (optimized for the species way of life)
- also some variation within species, but generally within the same range
- e.g. hearing range, visual range
17
Q
True or false: sensory receptors are evenly distributed across the body and its organs
A
False
18
Q
What is receptor density important for?
- Provide an example
A
Determining the sensitivity of a sensory system
- e.g. more tactile receptors on the fingers than on the arm
19
Q
Differences in receptor density determine what about animals? Provide an example
A
The special abilities of many animals
- e.g. olfactory ability of dogs
20
Q
Define transduction
A
Changing a physical stimulus (analog signal) into a neural (digital) signal
21
Q
Describe the initial stage of sensory processing (at the receptor)
A
Change in electrical potential of the receptor cells creates a generator potential (IPSP or EPSP)
- A graded response to a stimulus, or a graded depolarization induced in the terminal of a sensory receptor, which after achieving a threshold level, is capable of producing an action potential in the afferent axon in the nearby sensory neuron (think graded potential or EPSP)
22
Q
What is the vibration detector in our skin? Describe its structure
A
Pacinian corpuscule
- Free nerve ending surrounded by an onion-like structure
23
Q
Describe how vibrations are detected through Pacinian corpuscles
A
Stretching the membrane through vibrations opens stretch-activated Na+ channels.
- Vibrations produce graded potentials proportional to intensity of stimulus (intense enough produces action potential)
24
Q
What are 6 general features of sensation that apply to most of our senses?
A
- Coding
- Adaptation
- Pathways
- Suppression
- Receptive fields
- Attention
25
Sensory information is encoded by what?
Action potentials
26
How does the neuron code for the duration/intensity of a stimulus in general?
Sensitive range vs. discrimination threshold (what the neuron is sensitive to, vs. how neurons discriminate between different senses)
27
In general, the sensitive range of each sensory receptor is wider than the response repertoire of a single cell. How is this resolved? What is this called?
Multiple parallel neurons with different thresholds are recruited.
- This results in a higher neural response rate to higher (greater range of) stimulus intensity
- Called: range fractionation
28
Define sensory adaptation
Sensory receptors detect change, but ignore unchanging events to simplify sensory flow (e.g. wearing clothes)
- Response can change (reduce) despite constant stimulation
29
In terms of sensory adaptation, the response can be which two things?
Phasic or tonic
30
Describe phasic response
Change in frequency with constant stimulus
- i.e. neuron STOPS firing when stimulus becomes constant
31
Describe tonic response
Maintains response rate
- i.e. neuron continues firing at a constant rate when there's a constant stimulus (helps you maintain awareness of constant conditions, like body position or pain)
32
Each sense has a specific hierarchy. What are pathways made up of? What is the importance of each level?
Distinct non-overlapping nuclei or regions
- Each level serves a specific function
33
Which brain region gets the most sensory input? What does it do with this information?
Thalamus gets the most sensory input. It sends it to the cortex
34
True or false: There are specific cortical regions for each sense
True
35
Receptors from sensory peripheral nerves first send the information to which body part?
The spinal cord
36
Receptors from sensory cranial nerves first send the information to which body part?
The brainstem
37
Information sent to the brainstem have the option of going where? (2)
Either to the midbrain first or directly to the thalamus (before communicating with primary sensory cortical areas, and nonprimary sensory cortical areas afterwards)
38
How are cells in cortical areas that respond to given senses arranged (in general)?
In an orderly fashion (like a map)
39
Describe the primary cortex
Most input goes here, and this area projects to others
40
Describe the secondary cortex
Gets input from primary cortex, processes specific aspects of stimulus
41
Define receptive field and its general structure
The region of the sensory organ to which a particular neuron will respond
- Usually exhibit a center-surround arrangement (i.e. stimulus on center has highest response, while stimulus in surround has lower response
42
True or false: neurons at each level of hierarchy have receptive fields
True, and they progressively get more complex
43
What are two forms of suppression sensory input? Provide examples
1. Use of an accessory system to decrease input (e.g. closing eyes)
2. Descending pathways (e.g. neural inhibition of the receptor's activity)
44
Attention is difficult to define. What are 3 terms that could be used to describe it?
1. Alertness
2. Attuned to inputs
3. Focus on one stimulus
45
What is the cingulate cortex involved in?
Focusing on one stimulus (related to attention)
46
What is the posterior parietal (association) cortex involved in? What cells are found here?
Integrating sensory information to guide movement and attention.
- Poly modal cells
47
What does damage to the posterior parietal association cortex result in?
Neglect: a disorder where a person ignores stimuli on one side of their body or the environment
- Affects usually one side of the body = contralateral neglect
48
True or false: olfaction is widely variable among people
True; there are some specific anosmias (smell "blindness")
49
In general (males/females) have a better sense of smell
Females
50
Olfactory sensitivity decreases with what?
Age
51
What can affect olfactory sensitivity? Provide an example
Environment
- Smokers usually have poor olfactory abilities
52
Approximately how many receptors are found in the olfactory epithelium?
6 million
53
What is the approximate surface area of the olfactory epithelium?
2 cm^2
54
Each receptor on the olfactory epithelium has... (3)
1. Long dendrite that extends to the epithelial layer
2. Many fine cilia along epithelial surface
3. Fine unmyelinated axons that project through the cribiform plate and synapse in the olfactory bulb
55
True or false: Like typical neurons, the olfactory epithelial receptors are not replaced
False; they are constantly replaced throughout life (exception to the rule that neurons are post-mitotic)
56
What do olfactory receptors innervate and where?
They innervate mitral cells in particular glomeruli located in the olfactory bulb
57
True or false: Multiple types of olfactory receptor neurons input to each glomerulus
False; only one type of olfactory receptor neuron inputs to each glomerulus
58
Describe the 4 steps of olfactory transduction
1. Odorant molecule binds GPCR
2. Active G protein activates adenyl cyclase
3. Adenyl cyclase hydrolyzes ATP to cAMP
4. cAMP activates Na+ channels
59
Humans have about ____ different olfactory receptors. however, only _____ are functional
1000, 350-400
60
We only have about 350-400 functional olfactory receptors, but we can smell 5000 different odors. Explain how this is possible
Pattern coding
- Each particular odorant activates an array of receptors.
- Different combinations detect different odors
61
What is the only sense which does not need to go through the thalamus en route to the cortex?
Olfaction
62
Olfaction directly innervates which areas in the brain?
Areas involved in emotion (e.g. Amygdala)
63
What is the prepyriform cortex?
Part of the primary olfactory cortex, the cortical brain regions that receive mitral cell axon projections (process olfactory information)
64
True or false: olfactory mitral cell projections are topographical
True; olfactory receptors are arranged in an orderly fashion in the epithelium, and this ordered arrangement is preserved throughout the CNS
65
Describe what happened to Amazon candle reviews after COVID-19
Average scented candle reviews went down (for the top 3 scented candles on Amazon) because people complained that they couldn't smell them anymore (recall loss of smell being a symptom of COVID)
66
Describe what caused COVID-19 anosmia
Olfactory receptor cells do not have the ACE2 receptor (the binding site of SARS-CoV-2 virus)
- But critical support cells (sustentacular cells) have a lot of ACE2 receptors
- COVID-19 therefore damages the olfactory epithelium, resulting in a major loss of cilia
67
Define taste
The perception of the sensory cells in your taste buds
68
True or false: taste=flavour
False; flavour also involves the sense of smell
69
True or false: there's a lot of variability in taste perception between species
False; there's not a lot of variability in taste perception between species
- Exceptions: cats can't taste sweet, but snails can
70
True or false: Taste sense is present early in life
True; babies (even premature) will suck at sweet liquids and spit out bitter ones
71
When does the salty sense develop? It is not ____-dependent
In the first few months; experience (i.e. develops naturally)
72
Where are taste receptors found in general?
In special cells called taste cells
73
Many taste cells group together to form...
An onion-like structure known as a taste bud
74
Thousands of taste buds are found in....
Nipple-like structures (called papillae at the upper surface of the tongue)
75
Other than our mouths, where else are taste receptors found?
In our throat and in our gut
76
What are the 5 different taste receptor types?
1. Sweet
2. Sour
3. Salty
4. Bitter
5. Umami
77
What do each of the five taste receptor types respond to?
A different chemical component of food
78
What is taste transduction performed by?
Taste receptors found on papillae
79
Each papillae has ____ taste buds. Each taste bud has ____ cells and _____ receptor types
1 or more, 50-150, several
80
Taste buds are arranged with a______ and are _______
Pore at the end, recycled every 10-14 days
81
Besides taste receptors, what other receptors are on the surface of the tongue?
Nociceptors ("pain" receptors)
82
What are the 3 different papillae, and where are they located?
1. Fungiform (tip of the tongue)
- Most numerous
- One bud/papillae
2. Foliate (sides of the tongue)
3. Circumvallate (back of the tongue)
83
True or false: all different papillae detect different tastes
False; this is a myth. Each participate in transduction of all tastes (not the tip for sweet, sides for sour, etc)
84
Describe salty taste transduction
Salt detected by Na+ ion channel (because salt=NaCl)
- Na+ from salt enters cell, depolarizes it
85
Describe sour taste transduction
Hydrogen ions (H+) from sour taste block K+ leak channels.
- K+ cannot leave the cell, causing it to depolarize
86
Describe sweet taste transduction
Special GPCRs are activated, causing the phosphorylation and closure of K+ channels (resulting in depolarization)
87
Describe bitter taste transduction
Special GPCRs with 30 different receptor subtypes
- Results in either the decreased opening of K+ channels, or the opening of Cl-/non-specific channels
- Some people can't taste some types of bitter
88
Describe umami taste transduction
Type of glutamate receptor (GPCR)
- Responds to certain amino acids
- MSG (monosodium glutamate), which is a flavour enhancer added in certain food but also found naturally in some foods (e.g. tomatoes and cheese) activate this GPCR
89
What are the 3 cranial nerves involved in taste?
1. VII (facial nerve)
2. IX (glossopharyngeal nerve)
3. X (vagus nerve)
90
What is the general brain pathway for taste? (3)
Brainstem -> thalamus -> cortex
91
True or false: the central pathway for taste perception is as simple as labelled lines
False; taste perception is caused by pattern coding and the relative activity of different incoming signals
92
The visual system turns _____ into ______
Light energy, a neural signal
93
Describe light energy (2)
- Electromagnetic energy of specific wavelengths
- Can be direct (looking at source) or reflected (wavelengths reflected off an object)
94
True or false: the visual range is constrained by biology
True; range is constrained by biology, not a property of the light itself
95
What are the 5 eye parts involved in light processing?
1. Cornea
2. iris
3. Lens
4. Retina
5. Muscles
96
Describe the retina in general (3)
- Composed of photoreceptors and various neurons
- Built backwards, light passes through translucent neurons before reaching photoreceptors
- Converts received light into neural signals and send these signals on to the brain for visual recognition
97
What 4 things must the retina do?
1. Must convert (transduce) light energy into action potentials
2. Must discriminate different wavelengths (colours)
3. Must work over a wide range of light intensities
4. Must perceive minute details
98
What are the 3 layers of the retina in general?
1. Photoreceptors (rods/cones)
2. Bipolar cells
3. Ganglion cells
99
What are the two types of photoreceptors, and what do each of them detect?
1. Rods: Dim light
2. Cones: Colour; bright light
100
In general, how are photoreceptors arranged?
Outer segment, inner segment, synaptic terminal
101
Describe the blind spot in the eye
Backwards structure produces a blind spot.
- Blood vessels and axons that make up the optic nerve leave eye through optic disc.
- This is an area free of photoreceptors, produces a hole in the lateral receptive field that is filled in by the other eye (also filled in by the brain when only one eye is in use, no physical hole is perceived)
102
Describe the fovea in the eye (4)
- Center of focal point
- Part of the retina with the best acuity
- Only cones, no rods
- Better ratio of photoreceptor cells to ganglion cells in the fovea (1:1, could be 1:100 or more in periphery) so photoreceptors are not obscured by ganglion cells
103
How many photoreceptors are there in general?
4
104
What is opsin?
Light sensitive photopigment found in both rods and cones
105
What is the photopigment in rods?
Rhodopsin
106
How many photopigments are there for each type of cone?
3; one for each type of one (and there are 3 types of cones)
107
True or false: each of the photopigments are best activated at specific wavelengths
True
108
What wavelength does the S cone show maximum response at, and what colour does it detect?
419 nm, blue
109
What wavelength does the Rod show maximum response at?
496 nm
110
What wavelength does the M cone show maximum response at, and what colour does it detect?
531 nm, green
111
What wavelength does the L cone show maximum response at, and what colour does it detect?
559 nm, red
112
In humans, __ different alleles exist for red, ___ and ___
- What does this mean?
2, 552 nm, 557 nm
- humans perceive red as slightly different
113
What type of receptor is opsin, and what is it bound to?
GPCR, bound to a light-absorbing chromophore, 11-cis-retinal (derived from Vitamin A, which is in carrots)
114
Phototransduction in photoreceptors involves which 3 main biochemical events?
1. Light stimulation of opsin in the receptor discs leads to the activation of a G-protein (TRANSDUCIN)
2. The GTP-bound alpha subunit of transducin activates a phosphodiesterase (PDE)
3. The activated phosphodiesterase (PDE) hydrolyzes cGMP into GMP, reducing its concentration in the outer segment of the photoreceptor and leading to the closure of sodium channels in the outer segment membrane. This causes HYPERPOLARIZATION of the membrane
115
During phototransduction, the outer segment membrane (depolarizes/hyperpolarizes)
Hyperpolarizes
116
What does light-induced hyperpolarization of the membrane in rods and cones result in?
A reduction of glutamate release, which affects post-synaptic bipolar cells
117
(more/less) glutamate is released by photoreceptors in the light, while (more/less) glutamate is released by photoreceptors in the dark
Less, more
118
How are on-center bipolar cells affected by a greater glutamate release from photoreceptors (in the dark)? What do they express?
They hyperpolarize in response to glutamate (they express metabotropic mGluR6 receptors that are inhibited by glutamate)
119
How are off-center bipolar cells affected by a greater glutamate release from photoreceptors (in the dark)? What do they express?
They depolarize in response to glutamate (they express ionotropic receptors that are excited by glutamate)
120
Glutamate released by photoreceptors (inhibits/activates) "on-center" bipolar cells, while it (inhibits/activates) "off-center" bipolar cells
Inhibits, activates
121
Describe what happens to "on-center" and "off-center" bipolar cells in the presence of light, and how this impacts ganglion cells
- "On-center" bipolar cell deploarizes and activates ganglion cells
- "Off'center" bipolar cell hyperpolarizes and reduces activity of the ganglion cells
Note: the main difference between on-center/off-center bipolar cells is different receptors for the neurotransmitter glutamate, leading to two separate but parallel pathways for processing visual information.
122
Describe retinal ganglion cells (4)
- Don't see shapes
- They have very small dots as receptive fields
- Respond to the presence or absence of light
- Classic center/surround receptive field
123
Retinal ganglion cells can be what two structures?
- On-center/off-surround
- Off-center/on-surround
124
How do retinal ganglion cells receive input from many photoreceptors?
Via bipolar cells
125
What does a ganglion cell's response depend on?
Where in its receptive field it is stimulated
126
Stimulation in the center of on-center bipolar/ganglion cells (increases/decreases) the firing rate of ganglion cells
Increases
127
Stimulation outside the center of on-center bipolar/ganglion cells but within the receptive field (increases/decreases) the firing rate of the cell
Decreases
128
Retinal ganglion cells have overlapping cells. What does this result in?
One photoreceptor can contribute to many receptive fields
- Can be in the on-area of one ganglion cell and in the off area of another ganglion cell
129
Describe how the visual system detects edges (and ultimately, shapes)
The visual system can detect edges by monitoring the activity of adjacent receptive fields
130
Where does the right field of vision go towards?
Goes to left halves of retinas and left hemisphere
131
Where does the left field of vision go towards?
Goes to right halves of retinas and right hemisphere
132
Describe how the visual fields are "connected" (2)
- Each cortex "sees" only half of the visual field. The 2 fields overlap, and information is exchanged over the optic chiasm.
- The corpus callosum connects the two hemispheres but only certain brain structures
133
Describe the hemisphere connections between the frontal lobes and the occipital lobes
- Most of the frontal lobes are connected to one another
- The occipital lobes have almost no callosal connections (exception: cells that lie along the midline of the visual field are connected to one another via the callosum so that their receptive fields overlap)
134
What are the 4 major targets of retinal ganglion cells (i.e. where the optic nerves go)
- Describe what they are part of, and what they detect
1. Superior colliculus (part of the midbrain; coordinates and detects movements)
2. Lateral geniculate (part of the thalamus; vision)
3. Suprachiasmatic nucleus (SCN; part of the hypothalamus; important for the circadian clock)
4. Pretectum (pupil and lens reflexes)
135
True or false: each ganglion cell "sees" only a little bit of the visual world.
True
136
The visual field is made up of ____ of overlapping receptive fields
1000s
137
Describe how retinal ganglion cells project to the brain
Project from the retina to the brain in an orderly fashion, preserving their spatial arrangement
138
What are the 2 types of ganglion cells?
1. M cells (magnocellular)
2. P cells (parvocellular)
139
Describe M cells (4)
- Large cells
- Receive inputs from RODS
- All over retina
- Very sensitive, but colour blind
140
Describe P cells (4)
- Small cells
- Receive inputs from CONES
- Mostly in fovea (best acuity)
- Colour sensitive, perceive fine detail
141
True or false: M and P cell pathways are segregated throughout the visual system
True
142
What are the 3 main routes (systems) to the visual brain?
1. Tectopulvinar system
2. Geniculostriate system
3. Retinohypothalamic tract
143
Describe the tectopulvinar system (4)
- Some M cell axons
- Gets info from the retina and takes it to the Superior colliculus in the tectum
- Superior colliculus cells project ot pulvinar nuclei in in the thalamus
- This projets to parietal and temporal cortex
144
What does the tectopulvinar system do?
Analyze and coordinate movements (i.e. detects things that move)
145
Describe the Geniculostriate system (2)
- LGN receives input from the P pathway (cones) and some of the M pathway (rods)
- Gets info from the lateral geniculate and sends it to layer IV of visual cortex
146
Describe the Retinohypothalamic tract (2)
- Light sensitive retinal ganglion cells (pRGCs)
- Gets info from the retina and sends it to the SCN (responsible for circadian rhythm)
147
Describe the lateral geniculate (LGN) structure in the geniculostriate system
6 separate layers
- 1-2 magnocellular layers (rods)
- 3-6 parvocellular layers (cones)
148
Magnocellular cells (M-cells) send their projections to layers _____, and parvocellular cells (P-cells) send their projections to layers _____ of the lateral geniculate nucleus
1 and 2; 3 to 6
149
Each layer of the LGN in the geniculostriate system gets input from only...
One eye
150
Which 3 layers of the LGN receive visual information contralaterally?
1, 4, 6
151
Which 3 layers of the LGN receive visual information ipsilaterally?
2, 3, 5
152
What does the information from the geniculostriate system project to?
The striate cortex (primary visual cortex, aka V1)
- specifically, layer IV
153
Left/right segregation is preserved in the geniculostriate system, when the LGN projects to layer IV of the striatum. What does this lead to?
Ocular dominance columns in V1 (neurons in the visual cortex that respond preferentially to input from one eye or the other)
154
The receptive fields of all the ganglion cells that project to the LGN sum to what?
A receptive field in the LGN (each cell in the LGN also has a receptive field. The receptive fields of many LGN cells combine to form the receptive field of a single V1 cell)
- Larger fields that are observed than with a single ganglion and/or LGN cell
155
Which area(s) of the visual cortex form(s) the striate cortex/primary visual cortex?
V1
156
Which area(s) of the visual cortex form(s) the extrastriate or secondary visual cortex?
V2, 3A, 3B, 4 and 5
157
True or false: each area of the visual (occipital) cortex has a specific function
True
158
LGN topography is maintained in...
Area V1
159
Cortical cells (in V1) receive ____ input from _____
Convergent, numerous LGN cells
160
True or false: all visual space is equally represented in the visual cortex
False; not all visual space is equally represented, the fovea is disproportionally represented
161
Describe the orientation of the visual world in the visual cortex
The visual world is flipped around
- The top of the visual field is represented in more ventral visual cortex regions
162
Describe the dorsal visual stream
Visual processing pathway from V1 to the parietal lobe
- "how" you react; controls movement to or away from stimulus
163
Describe the ventral visual stream
Visual processing pathway from V1 to the temporal lobe
- "what"; identifies the stimulus
164
True or false: Both the geniculostriate and tectopulvinar pathways contribute to both the dorsal and ventral visual streams
True; there are cross connections between them
165
What are mirror neurons?
Fire when moving an object, or when watching someone move an object
166
Within V1, processing is grouped into which three clusters?
1. Cortical columns
2. Blobs
3. Interblobs
167
What are blobs in the V1 cortical region?
Clusters of cells that respond to colour
168
What are interblobs in the V1 cortical region?
Clusters of cells that respond to form and motion
169
In the V2 cortical region, processing is grouped into which three clusters?
1. Thin stripes
2. Thick stripes
3. Pale zones
170
What do thin stripes in V2 respond to?
Colour (they get info from the blobs in V1)
171
What do thick stripes in V2 respond to?
Motion (they get info from the interblobs in V1)
172
What do pale zones in V2 respond to?
Form
173
Blobs and stripes are revealed with a stain that is proportional to...
Metabolic activity
174
True or false: Segregation of function is preserved throughout the visual system
True
175
What does the V3 cortical region detect? What does it gather information from and send information to?
Detects form (3A form, 3B dynamic form)
- V3A gathers info from the thick region in V2, while V3B gathers info from thin region in V2
- V3A sends info to parietal lobe, while V3B sends info to temporal lobe
176
What does the V4 cortical region detect? What does it gather information from and send information to?
Detects colour
- Gathers info from extrastriate cortex (V2)
- Sends info to the temporal lobe
177
What does the V5 cortical region detect? What does it gather information from and send information to?
Detects motion
- Gathers info from the extrastriate cortex (V2)
- Sends info to parietal lobe
178
Describe the receptive fields of primary visual cortex (V1) cells
They have larger receptive fields because they receive input from an array of LGN cells (and thus retinal ganglion cells) that overlap
- on/off arrangement
- Respond best to bars of a particular orientation
179
How are V1 neurons most excited?
Through the stimulation of a subset of ganglion cells, perfectly on the on region
180
The visual cortex is arranged in such a way that... (2)
- All cells within a column respond to the same stimulus
- Cells in adjacent columns respond to similar stimuli but slightly different line orientation
181
What are the 3 types of cells in the V1?
1. Simple cells
2. Complex cells
3. Hypercomplex cells
182
Describe simple cells in V1
Act as orientation detectors
- has strongest response when light falls on "on arrangement"
- e.g. horizontally preferred orientation vs. oblique-preferred orientation in simple cells
183
Describe complex cells in V1
Maximally excited by bars of light moving in a particular direction
184
Where are complex cells found?
Not only in the primary visual cortex (V1), but also in V2 and V3
185
Describe hypercomplex cells in V1
Are like complex cells, in that they are maximally excited by bars of light moving in a particular direction
- However, have both excitatory and inhibitory portions of the visual field (i.e. light can more from on to off receptor field)
186
What is the specific function of the primary visual cortex (V1)?
Processes simple forms. Also involved in forming mental images (activated during imagining a visual object)
187
What is the specific function of area V2 of the extrastriate cortex?
Responds to many aspects of vision, similar to V1.
- However, also has higher order integration, so will respond to complex relations among parts of the visual field.
- Responds to illusory contours (aka subjective contours: visual illusions that evoke the perception of an edge without a luminance or colour change across that edge)
188
What is the specific function of area V3 of the extrastriate cortex?
- Also describe what we know about areas V3A and V3B
Not well-defined, and a consensus on definition still needs to be reached. But we do know:
V3A (involved in the dorsal stream)
- Receives input from V2 and from the primary visual area and projects to the posterior parietal cortex
- Processing of global motion and form
V3B (involved in the ventral stream)
- Weaker connections from the primary visual area, and stronger connections with the inferior temporal cortex
- Colour and dynamic form
- Processing of colour and dynamic form
189
What is the specific function of area V4 of the extrastriate cortex? (2)
- Responds best to complex stimuli (e.g. weird forms)
- colour perception
190
What is the specific function of area V5 of the extrastriate cortex? (2)
- Responds best to motion
- Clinical cases of V5 damage (Akinetopsia; "motion blindness". Individuals with akinetopsia perceive moving stimuli as a series of stationary strobe-like images and see visual trails behind moving objects instead of continuous movements)
191
What does the wide variety of colour vision abilities between different species relate to?
Diurnal-nocturnal life
192
Describe excellent trichromatic colour vision and provide an example
3 cones
- e.g. humans
193
Describe robust dichromatic colour vision and provide examples
2 cones
- e.g. dogs, pigs
194
Describe feeble dichromatic colour vision and provide examples
2 cones, but few in number
- e.g. cats
195
Describe minimal colour vision and provide examples
Nocturnal animals, single cone compared to rods (lots of rods)
- e.g. mice, rats, raccoons
196
In humans, ___% of males are relatively or completely deficient in colour vision
7-8
197
In humans, ___% of females are relatively or completely deficient in colour vision
0.5%
198
What is the most common form of colour blindness?
Deuteranopia (red-green colourblind)
199
Humans with deuteranopia and mammals with poor colour vision are unable to differentiate between which colours?
Red and green
200
Describe trichromatic theory
Based on the fact that there are 3 sets of cones, simply combining differential activation of different cones yields colour response
- Entire range of colours can be achieved by mixing various amount of the 3 primary colours red, green and blue
201
According to the trichromatic theory, full 100% activation of each type of cone results in what?
White light
202
Blue-green corresponds to what wavelength?
475 nm
203
Orange corresponds to what wavelength?
600 nm
204
Deep red corresponds to what wavelength
700 nm
205
Describe the max response of cones in response to blue-green
20% short (blue curve)
65% medium (green curve)
40% long (red curve)
206
Describe the max response of cones in response to orange
0% short (blue curve)
25% medium (green curve)
75% long (red curve)
207
Describe the max response of cones in response to deep red
0% short (blue curve
0% medium (green curve)
5% long (red curve)
208
Describe the Opponent process theory (in general)
Based on visual experience, it was proposed by Hering that colours were perceived in a balance of three pairs, Red/Green, Blue/Yellow and Black/White (brightness)
209
According to the opponent process theory, colour balance occurs at what level? Describe the arrangement of the ganglion cells in general according to this theory
The level of the ganglion cell (not at the level of the cones)
- Some cells of the visual system are excited by one of the opponent colours and inhibited by the other
- Center-surround arrangement (i.e. yellow is activated by both red and green cones)
210
Describe Red center/green surround opponent process theory
Center: activated by red, inhibited by green
Surround: activated by green, inhibited by red
Ganglion cell:
- Maximal activation: red on center and green on surround
- Maximal inhibition: green on center and red on surround
211
Which of trichromatic or opponent process theory is correct?
Both trichromatic and opponent process theories are both accurate and play a role in colour vision
- Trichromatic: explains how the photoreceptors (cones) work
- Opponent process: explains how colour is handled throughout the rest of the CNS
212
Describe "The Dress"
The context, or surroundings, in which an object we are looking at appears in, influences our perception of its colour.
- If you assumed that the dress was in a shadow in natural light, you would see it as white and gold because your brain automatically subtracted blue-ish short-wavelength light
- If you see the dress as blue and black, you subtracted the longer wavelengths (red) to align with the assumption that the photo was taken in warm, artificial light
213
True or false: all sound moves at the same speed
True; 340 m/s
214
What does sound differ in?
Frequency
215
What is frequency, and what does it correspond to? What is it measured in?
Vibration rate (how many cycles/unit time), corresponds to our perception of pitch (high frequency=high pitch)
- Measured in Hz
216
What is the human frequency hearing range?
~20-20,000 Hz
217
Describe the Doppler effect
Source pushes sound thereby increasing its frequency as it approaching. Opposite happens as it passes, frequency drops
218
Describe amplitude, and what it is measured in
Difference in perceived intensity of sound (loudness)
- measured in decibels (dB)
219
Describe what happens to frequency and amplitude when you hit a tuning fork soft and hard
Hit it soft: produces a certain frequency
Hit it hard: change in amplitude but produces the same frequency -> no change in pitch
- Wavelength is the same, but the amount of air moved is greater (increased compaction of air, more energy in the sound wave)
220
True or false: hearing can be injured by frequent exposure to high intensity sounds (>100 dB) like guns, construction and music
True
221
What is Tinnitus?
Ringing ears, which can affect your hearing, particularly at low intensities
222
Describe simple sounds
Pure tone; only produces one frequency
223
For sound, the rate at which a complex waveform repeats is called its:
Fundamental frequency
224
Describe complex sounds
Made up of a combination of frequencies: 1 fundamental frequency, many overtones
225
What is an overtone?
Multiples of fundamental frequency, each with its own intensity (amplitude)
226
True or false: complex tones are periodic
True
227
Noise is...
Aperiodic
228
What is the auditory system's task?
To convert air pressure changes into neural activity
229
What 5 things must the auditory system be able to do?
1. Discriminate similar frequencies
2. Detect weak sounds
3. Detect many sounds at the same time
4. Analyze sounds to decipher language and meaning
5. Localize sound to orient towards source
230
What 3 parts is the ear made of?
1. Outer ear
2. Middle ear
3. Inner ear
231
The outer ear is made of what three parts?
1. Pinna
2. External ear canal
3. Tympanic membrane
232
Describe the pinna (3)
- Funnel-like part, made of cartilage and flesh
- Designed to catch sound waves and deflect them into the external ear canal
- Modifies sounds (enhances certain frequencies)
233
Describe the external ear canal (3)
- Passage through skull
- Amplifies sound waves
- Focuses them onto the ear drum
234
Describe the tympanic membrane (2)
- Ear drum
- Vibrates based on frequency of sound waves
235
Describe the middle ear in general (2)
- Air-filled chamber
- Contains ossicles and muscles (muscles stiffen the system)
236
What are the three ossicles (in order)?
1. Malleus ("hammer")
2. Incus ("anvil")
3. Stapes ("stirrup")
237
Describe the ossicles in general (3)
- Connected in series
- Amplify vibrations
- Connect ear drum to cochlea
238
Describe the eustachian tube (3)
For the ear drum to work efficiently, air pressure in the MIDDLE EAR must match the pressure in the outer ear
- Eustachian tube equalizes the pressure (connected to nasal-sinus cavity)
- e.g. swallowing to equalize pressure on an airplane
239
What causes the loss of hearing sensitivity when you have a cold?
Loss of hearing sensitivity when you have a cold, eustachian tube clogged
240
The inner ear is made up which 3 things?
1. Semicircular canals
2. Oval window
3. Cochlea
241
Describe the semicircular canals (3)
- Vestibular organ
- Detect head orientation and acceleration
- Critical for balance
242
Describe the oval window (2)
- A membrane-covered opening in the inner ear; connects the middle and inner ear
- Sound vibrations are transmitted from the stapes bone to the fluid-filled cochlea
243
Describe the cochlea (2)
- Structure that transduces sounds into neural code (sound waves -> action potentials)
- Coils around self -- looks like a snail's shell
244
How does the inner ear connect to the brain?
Through the auditory nerve (VIIIth cranial nerve)
245
What is the transduction machinery in the cochlea?
The Organ of Corti
246
What is the Organ of Corti divided into?
1. Basilar membrane
2. Tectorial membrane
3. Hair cells
247
What are the two different types of hair cells in the Organ of Corti, and what is the main difference between them?
1. Inner hair cells
2. Outer hair cells
- outer hair cells connected to tectorial membrane
248
How many stereocilia are found on hair cells?
50 to 200 (hair-like projections on the surface of sensory hair cells in the inner ear that are crucial for hearing and balance)
249
Describe how inner and outer hair cells are arranged in the organ of Corti
1 row of inner cells, 3 rows of outer cells
250
Describe inner hair cells (3)
- Approximately 3500
- Responsible for hearing
- Not connected to tectorial membrane
251
Describe outer hair cells (3)
- Approximately 12,000
- Mechanically amplify low-level sound entering the cochlea
- Connected to tectorial membrane
252
The (base/apex) of the basilar membrane responds to higher pitches (higher frequencies)
Base
253
The (base/apex) of the basilar membrane responds to lower pitches (lower frequencies)
Apex
254
What is meant by the tonotopic organization of the basilar membrane?
The base and apex of the basilar membrane respond to different frequencies/pitches
255
What does the amount of displacement of the basilar membrane at any point vary with?
The frequency
256
Where is the maximal neural response in hair cells, relative to the basilar membrane?
Maximal neural response in hair cells located at the part of the basilar membrane where you observe the peak displacement
257
Describe the basilar membrane width/thickness near the oval window (base)
Narrow and thick
258
Describe the basilar membrane width/thickness near the apex
Thin and broad
259
True or false: the basilar membrane is sensitive and enhances small frequency differences
True
260
What is Volley theory?
At the apex of the basilar membrane, frequency is not coded in a tonotopic fashion (<200 Hz, low frequency)
- All hair cells can respond
- So action potential rate is proportional to frequency (higher frequency=higher firing rate
261
Sound vibrations cause the basilar membrane to...
Move. This motion causes the tectorial membrane to shear against the hair cells, bending their cilea (hair bundles)
- even though the inner hair cells don't touch the tectorial membrane, the cilia still do.
262
Describe sound transduction from the stapes to the tectorial membrane (3)
1. Pressure of the stapes (stirrup) on the oval window pushes the fluid in the cochlea
2. The movement of the fluid inside the cochlea causes the basilar membrane to move
3. This causes the cilia of the inner hair cells to move back and forth against the tectorial membrane
- This results in changes of membrane potential of the hair cells and signal transduction
263
(Inner/outer) hair cells are responsible for hearing
Inner
264
What does the selective loss of inner hair cells lead to?
Complete loss of hearing
265
___% of afferent fibers (signal towards the CNS) in the auditory nerve come from inner hair cells
90-95%
266
Describe how bending cilia changes membrane potential (3)
- Physically open various ion channels (no ligands or voltage changes required, e.g. mechanoelectrical transduction (MET) channel; K+ current)
- Each stereocilia is tethered to its neighbour
- When they bend, they pull open cation channels
267
Hair cell mechanoreceptors rely on ionic gradients with a unique organization in the inner ear: they allow the flow of __ into cells. This is due to what?
K+
This is due to an unusually high K+ concentration in the major fluid spaces of the cochlea (outside of the cells), which is opposite from usual (K+ is usually higher inside the cell)
268
Describe what happens when cilia is bent toward the tallest cilium
Opening of K+ channels -> influx of K+ -> depolarization => activation of voltage-gated Ca2+ channels -> increase in NT release
269
Describe what happens when cilia is bent toward the shortest cilium
Hyperpolarization = decreased NT release
270
If the inner hair cells transduce sounds, what do the outer hair cells do? (4)
1. Send axons (afferents) to nuclei in the brain stem
2. Receive feedback from brain (efferent information) that regulate hair cell activity (indicates if you need to fine tune or move closer to a sound source)
3. Contract and relax in response to signals from the brain
4. Changes the stiffness of regions of the basilar membrane
- Sharpens tuning for some frequencies
271
What does each hair cell synapse onto?
One bipolar cell (each bipolar cell gets input from only one hair cell)
272
Axons of the bipolar cells in the auditory system form the...
VIIIth cranial nerve
273
Bipolar cells in the auditory system contact the (ipsilateral/contralateral) side of the brainstem, specifically the...
Ipsilateral, Cochlear nucleus
274
From the brainstem, auditory information is sent to...
Both halves of the brain
- Sensory info from the 2 halves is merged early on, unlike the visual system
275
How is the phase of a sound wave coded by the brain?
The bursting pattern of firing, which corresponds to the wavelength of basilar membrane movement
276
What does the cochlea innervate? (2)
The ipsilateral cochlear nucleus and the superior olivary nucleus (bilateral)
277
What does the superior olivary nucleus innervate in the auditory system?
The inferior colliculus, which is a major site of convergence in the auditory system
278
What does the Colliculus innervate?
The medial geniculate, which is a part of the auditory thalamus
279
What does the Geniculate innervate?
The primary auditory cortex
280
Where is the primary auditory cortex (A1) found, and what side of the brain is it bigger on?
Within Heschl's gyrus, larger on the right side of the brain
281
What is the primary auditory cortex (A1) surrounded by?
Secondary cortices
282
What are the secondary cortices in the auditory system specialized for? (3)
Particular types of sounds:
1. Localization in space
2. Movement of sound
3. Species-specific sounds
283
What is Wernicke's area part of, and what is it responsible for?
Part of the secondary (auditory) cortices
- Involved in language processing, written and/or spoken
284
Describe the size of Wernicke's area in right-handed people
Bigger on the left side of the brain
285
Describe the size of Wernicke's area in left-handed people
70% bigger on the left; 15% bigger on the right, 15% bilateral
286
Describe the dorsal stream from the auditory cortex
Dorsal stream to the posterior parietal cortex (PPC)
- Plays a role in auditory control of movement ("Where")
- e.g. reaching for a ringing phone or alarm clock in the dark
287
Describe the central stream from the auditory cortex
To further temporal lobe areas
- Plays a role in identifying auditory stimuli ("what")
288
What is meant by place coding of sound properties?
Idea that different parts of the basilar membrane have different peak vibrations for different frequencies (peak vibration at base for high frequencies and peak vibration at apex for low frequencies)
289
Given the 1:1 arrangement of hair cells to bipolar cells, the brain knows...
Exactly where on the membrane the hair cell was activated
290
Where is the frequency map of the basilar membrane preserved?
In the CNS, particularly in the inferior colliculus and the primary/secondary auditory cortices
291
Unlike vision, auditory information become ___ at lower levels of the CNS
- Explain how
Bilateral
- The cochlear nerve inputs to both sides of the brain (superior olivary nucleus)
292
What is coincidence detection in the auditory system?
The fact that the auditory information becomes bilateral allows the brain to compute the difference in arrival time between ears, allowing for sound localization
293
How does the brain locate the source of a continuous sound (after it has arrived at both ears)?
Brain can calculate the phase difference between sounds
294
What is a sound shadow?
High frequency sounds (>1500 Hz) get blocked, causing a sound shadow on the distal side of our head.
- The sound is less intense in one ear , so the brain uses this to calculate direction.
295
Do low frequencies produce a sound shadow?
No; low frequency sounds bend around our heads quite easily. Both ears will perceive the same loudness
296
What is conductive hearing loss, and can it be corrected?
Problem in the mechanics of the ear, it can be corrected
297
What are the three causes of conductive hearing loss?
All mechanical issues
1. Fluid in the ear
2. Ossicles may fail to conduct sound to the cochlea
3. Eardrum may fail to vibrate in response to sound
298
What is the most common cause of temporary hearing loss in children?
Ear infections
299
What is sensorineural hearing loss?
Problem with transduction of sound waves into action potentials
300
What are 5 causes of sensorineural hearing loss?
1. Genetic
2. Trauma
3. Infection
4. The antibiotic gentamicin kills hair cells
5. High doses of Aspirin can also cause temporary dysfunction in hair cells
301
What are 2 treatments of sensorineural hearing loss?
1. Cochlear implants
2. Experimental work with auditory brainstem implants
302
What is a cochlear implant?
An array of electrodes hooked up to a sound analyzer. Electrodes are surgically inserted into the cochlea.
- The electrodes stimulate a certain region of basilar membrane when certain frequency is detected.
303
True or false: cochlear implants are only used to treat children
False; they can be used to treat some children (2-6 years, the earlier the treatment, the better) and they can help adults who lost hearing later in life
304
What do cochlear implants require?
Intact auditory nerve and brain structures (because stimulating the cochlea would not work otherwise)
305
What is central deafness, and what could it result in?
Hearing loss caused by CNS damage
- Could result in the inability to perceive any sound or to perceive specific sounds (verbal or non-verbal deficit)
- Can still exhibit reflexive hearing, just no conscious perception
306
What is the vestibular sense?
Sense that gathers info regarding force of gravity and acceleration of the head. Allows for maintaining balance (posture & equilibrium) by monitoring motion of the head
307
What is the vestibular sense accomplished by? (3)
1. 3 Semi-circular canals
2. Utricle
3. Saccule
308
How is the vestibular sense related to the sense of vision?
It stabilizes the eyes relative to the environment
- When moving your head you can still keep an image focused on the retina
309
What does the utricle detect?
Linear acceleration in the horizontal plane
310
What does the saccule detect?
Linear acceleration in the vertical plane
311
What do the semicircular canals detect?
Angular force, such as rotation
312
How is transduction achieved in the vestibular system (in general)?
Accomplished by hair cells
- Each is arranged in specific orientations to respond to acceleration in a particular direction
313
Describe how transduction is achieved in the utricle and saccule specifically
Otoliths (calcium carbonate) sit on top of a gelatinous layer on top of hair cells, and they bend hair cells in the direction of gravity
- Subject to inertia and gravity (inertia causes endolymph to lag behind)
314
What happens to the endolymph in the vestibular system when the head first starts moving and when the head stops?
Initially stays still when the head moves (inertia)
- Endolymph keeps moving when the head stops
315
The semicircular canals are filled with endolymph. What does the endolymph resist?
Changes in momentum
316
What does the endolymph's resistance of change in momentum activate?
Hair cells in the ampulla when movements of the head and endolymph are different
317
True or false: The left and right semicircular canals response similarly to the same to movement
False; they respond differently
318
Disagreement between what you see and your head position can lead to...
Vertigo and nausea
319
You need to have coordination between which two things in somatosensation?
Sensory input (afferent) and motor output (efferent)
320
Define somatosensation
The ability to feel hot and cold, to recognize an object by touch alone, to respond to pain, to balance on a beam, etc.
321
What 3 categories of somatosensory receptors do we have?
1. Nociception
2. Hapis
3. Proprioception
322
What do nociception receptors detect? (2)
1. Pain
2. Temperature
323
What do hapis receptors detect? (2)
1. Fine touch
2. Pressure
324
What do proprioception receptors detect?
Body awareness, information about body movement and position
325
What is the area of the array of skin receptors?
1 to 2 m^2
326
What are the 3 layers of the of the skin that contains receptors?
1. Epidermis
2. Dermis
3. Subcutaneous (hypodermis)
- Not really part of the skin
327
Which receptors detect pain and temperature?
Free nerve endings
328
Which receptors detect touch (to some extent)? (4)
1. Merkel's disc
2. Meissner's corpuscle
3. Pacinian corpuscle
4. Ruffini's ending
329
Describe the structure of Pacinian corpuscles and what they detect
Free nerve-ending surrounded by an onion-like capsule
Detects vibrations of around 200Hz or more
330
How do Pacinian corpuscles depolarize?
Rapid deformations of capsule lead to stretching of the free-nerve ending, opening Na+ channels
331
Pacinian corpuscles have (small/large) receptive fields, and are (slow/fast) adapting
- explain what the adaptation speed means
Large, fast (don't detect vibrations after continuous stimulation)
332
Describe the structure of Merkel's discs and what they detect
Densely packed in skin areas wth fine spatial resolution. Respond to very light touch (e.g. mosquito landing on your arm)
333
Where are Merkel's discs predominantly found? (3)
The hands, lips, tongue
334
Merkel's discs are (slow/fast) adapting
- Explain what this means
Slow
- Keep being activated, as long as the stimulus is there
335
Describe the spatial resolution of Merkel's discs
Great spatial resolution, edge and point detection (e.g. know exactly where a mosquito lands on your arm)
336
Describe the structure of Meissner's corpuscles and what they detect
Densely packed in skin areas with fine spatial resolution; touch
337
Where are Meissner's corpuscles predominantly found? (3)
Hands, lips, tongue
338
True or false: Meissner's corpuscles are more numerous than Merkel's discs
True
339
Meissner's corpuscles are (slow/fast) adapting
Fast
340
What is the main difference between Meissner's corpuscles and Merkel's discs?
Meissner's corpuscles are fast adapting, while Merkel's discs are slow-adapting
- Merkel's discs also have better spatial resolution
341
Meissner's corpuscles respond to _____ which is important for ____.
Changing stimuli, determining texture detail
342
What do Meissner's corpuscles detect beyond touch/changing stimuli?
Edges, although spatial resolution is not as good as Merkel's discs
343
What do Ruffini's ending respond to?
Indentations/stretches in the skin when a body part is moved
344
Ruffini's endings are (slow/fast) adapting
Slow
345
Ruffini's endings have (low/high) spatial resolution
- What does this mean in terms of the size of receptive fields?
Low (aka large receptive fields)
346
Tactile information enters through the _____ root of the spinal cord. The signal then climbs the dorsal column and synapse in the ______.
Dorsal, medulla
347
After a tactile signal reaches the medulla, what happens to it?
The signal then crosses over to the other side of the medulla and ascends to the thalamus
348
What happens after a tactile signal ascends to the thalamus?
It then projects to the somatosensory cortex
349
What does the homunculus show in terms of what takes up a lot of space in the brain? What about what takes up little space?
Face, lips, tongue and hands take up a lot of space in the brain.
The limbs and trunk take up little space.
350
What does the homunculus reflect in terms of control?
Reflects level of control
- e.g. fine detail for mouth, rudimentary for chest
351
True or false: there's only a single homunculus
False; there are many parallel specialized maps for different parts of the brain.
- These areas feed into each other (perception is assembled from the integration of a simple sensation)
352
True or false: Receptive fields increase in size
True
353
Describe an example of sensory integration using the 3a and 3b areas for different fingers
- 3a and 3b might be for single fingers, but area 1 can be many fingers
- This info feeds into the 2' cortex, which merges with the dorsal stream
- 1' and 2' cortices feed into motor cortex, which guide movements
354
Describe plasticity within the cortical map
The cortical map can change/rearrange with experience or injury
355
Define pain
Unpleasant sensory and emotional experience associated with actual or potential tissue damage
356
Describe people who feel no pain
Can still feel (they touch system is still intact), just don't perceive injury (because touch and pain are different pathways)
- Suffer from a lot of injuries and tend to die young
357
What are the three purposes for pain?
1. Withdraw from source of injury
2. Promote restorative behaviours (sleep, feeding, grooming)
3. Social signal (elicit care-giving behaviour from others)
358
What is the peripheral origin of pain in general?
Tissue damage
- Causes the production/release of chemicals
- Activates adjacent nerve fibers
359
What 4 chemical signals activate nociceptors?
1. Serotonin
2. Histamine
3. Various neuropeptides
4. Prostaglandins
360
Nociceptors are...
Chemical or temperature receptors in the membrane of nerve fibers
361
Describe the pain pathway relative to the spinal cord
Goes through the dorsal root and crosses to the contraleteral side in the spinal cord
362
Describe pain reflex arc
Doral root from sensory neuron sends signal to interneuron. Interneuron both branches to the brain and synapses with motor neuron to retract away from source of pain
363
Describe the ascending/descending pain pathways (non-reflexive)
Primary afferent neuron activates a second order neuron in the spinal cord that goes to the brain. This synapses with the descending neuron in the brain that synapses with an inhibitory interneuron in the spinal cord. This inhibitory interneuron synapses with the primary afferent neuron.
364
How do general anesthetics work in general?
They interrupt nerve signals in the brain and body. This prevents your brain from processing pain
365
How do general anesthetics affect GABA receptors?
They are a GABA receptor agonist
366
How do general anesthetics affect NMDA receptors?
They are an NMDA receptor antagonist
367
How do general anesthetics affect 2-pore K+ channels?
They are 2-pore K+ channel activators
368
What are the 4 reversible effects of anethesia?
1. Immobility
2. Analgesia (inability to feel pain)
3. Amnesia
4. Unconsciousness
369
C-fibers and A-delta (Aδ) fibers are types of...
Free nerve endings
370
C-fibers are (myelinated/unmyelinated), and A-delta (Aδ) fibers are (myelinated/unmyelinated)
Unmyelinated, myelinated
371
What is the largest group of nociceptive receptors?
Transient Receptor Potential (TRP) channels
372
Describe the structure of Vallinoid receptor TRPV1 (aka VR1)
Like all TRP channels, a ligand-gated ion channel
373
What 6 things are TRPV1 receptors activated by?
1. Physical
2. Mechanical
3. Chemical
4. Heat
5. pH (<5.9, acids)
6. Various ligands (e.g. endocannabinoids, CAPSAICIN)
374
Hot and cold receptors are... (2)
Each on separate fibers and different receptors
375
What is one of the heat receptors?
TRPV1 (why spicy = hot and painful)
376
What is one of the heat receptors?
TRPV1
377
Other than heat, what is TRPV1 activated by?
Capsaicin (the "hot molecule in peppers, why spicy = hot)
378
True or false: Capsaicin is an adaptation in plants
True
379
What is one of the cold receptors?
Cool Menthol receptor (CMR1 aka TRPM8)
- on small fibers
380
What activates CMR1/TRPM8?
Menthol
381
Vallinoid-like (VRL) receptors are found on ____ and exhibit...
Large fibers, initial sharp pain (activated at a higher temperature)
382
What is the main difference between the touch and pain pathways?
Pain pathway crosses to the contralateral side of the spinal cord, while the touch pathway remains ipsilateral
383
Explain the gate control theory and why rubbing helps reduce acute pain
Painful stimuli activate slow, small C-fibers. This turns off inhibitory interneuron and activates the 2nd order neuron (activation pain pathway)
Touch stimuli (rubbing) activates fast large Aβ fibers which activates the inhibitory interneuron. This inhibits the 2nd order neuron (inhibition pain pathway)
384
Internal organs also have sensory receptors. Do they have their own pathways to the brain? explain
No. They synpase on spinal neurons that receive nocioceptive information from the body's surface
385
What input synapses with that of the heart causing pain to be detected in the brain (i.e. what can't the brain tell the difference between, converge at the dorsal root?)
left arm
386
What input synapses with that of the stomach causing pain to be detected in the brain (i.e. what can't the brain tell the difference between, converge at the dorsal root?)
Trunk
387
What input synapses with that of the kidneys causing pain to be detected in the brain (i.e. what can't the brain tell the difference between, converge at the dorsal root?)
Lower back
388
True or false: pain pathways can be activated midway along a nerve
True
389
What are the three types of muscles?
1. Cardiac
2. Smooth
3. Skeletal (Striated)
390
Describe smooth muscles (2)
- Contracts without any voluntary control
- Located in inner organs walls like bladder, intestine, stomach, blood vessels, etc
391
Describe skeletal (striate) muscles (2)
- Voluntary movement
- Fast twitch and slow twitch
392
How are skeletal muscles arranged?
In a reciprocal fashion
- antagonistic/synergistic (e.g. if biceps relax, then triceps contract)
393
What are skeletal muscles made up of? (3)
- 1000s of fibers
- Polynucleated cells (each cell has multiple nuclei)
- Contain myofibrils (made of actin and myoson)
394
Skeletal cells are _____ cells, stimulated by ____ at _____
Electrical, ACh, neuromuscular junction
395
What does the stimulation by ACh at skeletal muscles cause?
Produces an action potential, which causes fiber to contract (shorten)
- 1:1 response
396
True or false: Skeletal muscles have inhibitory synapses
False; muscles are turned off by the removal of Ca2+
397
Ca2+ needs to bind ____ to result in a contraction
Troponin
398
Describe the hierarchical control of movement
The basic CNS components are the neocortex, brainstem and spinal cord. Each level is able to exert a certain degree of control over muscles. Higher areas exert a greater degree of control. However, lower levels can regulate movements independent of higher areas, to a certain extent
399
Motor neurons are found in the _____ of the spinal cord
Ventral horn
400
Describe the arrangement of motor neurons
Project to muscles, and are topographically arranged in the spinal cord (neurons of the spinal cord are envisioned as a homunculus)
401
What are corticospinal tracts (CST) and what do they contact?
Pathways between the motor cortex and brain stem/spinal cord. They contact both motor neurons and interneurons
402
What do the axons that form the corticospinal tract mostly originate from? How are they organized?
Most of the axons that form the tract originate from pyramidal cells in layer V of the primary motor cortex, which descend into the brainstem.
- Most cross over to the contralateral side and continue down lateral corticospinal tract (CST).
- Some stay ipsilateral and continue down the ventral CST
403
Axons from layer V pyramidal cells in the motor cortex make synaptic connections with _____ in the spinal cord
Interneurons and motorneurons
404
What does sensory feedback for proprioception do?
Guides, refines, coordinates movements
405
What are the two muscle receptors?
1. Muscle spindle
2. Golgi tendon organ
406
What do muscle spindles detect?
Stretch of muscle
407
What do golgi tendon organs detect?
Tension
408
Describe the 5 steps for the stretch reflex
1. A disturbance is imposed
2. The muscle is stretched
3. Sensory fibers from the muscle spindle are activated
4. Excite motor neurons controlling stretched muscle (stimulate muscles to oppose stretch, aka contract)
5. Activate inhibitory interneurons (turns off antagonistic muscle from contracting)
409
What do spinal injury deficits depend on?
Level of damage
410
The spinal cord can to some extent regulate movements on its own, such as... (3)
1. Reflexes
2. Simple (extension or withdrawal)
3. Complex (walking, scratching)
411
True or false: The spinal cord can still generate movement, even after spinal injury
True, like with reflexes; there's just no conscious control of the movement
412
What did Fritsch and Hitzig do?
They electrically stimulated different areas of an anesthetized dog's brain
- Elicited different movements on the contralateral side of the body
413
What did Penfield do?
Mapped brain areas with much finer detail
- Carefully mapped the primary motor cortex (Brodmann's area 4, or precentral gyrus), topographically arranged
414
The motor cortex is arranged _____; adjacent body areas are controlled by ______
Topographically, adjacent brain areas
415
Complex behaviours involve complicated motor patterns. What was the old idea for how these were controlled?
Brain responded to constant feedback to direct movements
Move -> Feedback -> Anlayze -> Adjust -> Repeat
416
What did Lashley say?
Speed limits within the CNS are too slow for feedback to continuously regulate movements.
- Complex behaviours are broken into motor sequences (Movement modules preprogrammed by the brain and produced as a unit)
417
Describe the closed-loop control of movement (3)
- Uses feedback
- Maximizes accuracy
- usually involved in slow, smooth sustained movement
418
Describe the open-loop control of movement (3)
- Too fast to use feedback
- Ballistic movements (muscle contractions that exhibit maximum velocities and accelerations over a very short period of time. They exhibit high firing rates, high force production, and very brief contraction times)
- Anticipate error through experience and learning
419
What is the main function of the frontal lobe? How are functions organized here?
Plans, coordinates, and executes precise movements
- Functions are hierarchically organized
420
What are the 4 main areas of the frontal lobe?
1. Prefrontal cortex
2. Supplementary motor cortex
3. Premotor cortex
4. Primary motor cortex
421
Describe how functions are hierarchically organized within the frontal lobe (3)
1. Prefrontal formulates a plan of action
2. Prefrontal tells Premotor to coordinate required sequences
3. Premotor tells Primary Motor Cortex to initiate movements needed for selected program
422
Describe the prefrontal cortex (3)
1. Plans complex behaviours, not specific movements
2. Identifies goals that behaviours should be directed towards
3. Regulates activity of premotor area
423
Which part of the brain is responsible for planning and initiating movements?
Frontal lobe
424
Describe the Supplementary Motor area (2)
1. Planning movement based on memory
2. Implicit, rehearsal
425
What do lesions in the Supplementary Motor area cause?
Initiation of movement impaired
426
Describe the premotor area (5)
1. Produces complex sequences of movements
2. Selects motor programs appropriate for task
3. Coordinates simultaneous movements
4. Doesn't specify precise details of particular movement
5. Regulates activity of primary motor cortex
427
What do premotor lesions cause?
Premotor area coordinates simultaneous motor programs, and lesions abolish this.
- All movements possible, just loses coordination between them (e.g. Monkey with lesion is unable to catch object through a hole after pushing it though)
428
What is the primary motor cortex responsible for?
Executing skilled movements with fine detail
429
Complex movements depend on...
The primary motor cortex
430
What two grasps are controlled by the primary motor cortex?
1. Pincher grasp (requires primary motor cortex)
2. Power grasp (persists with damage to primary motor cortex)
431
Describe the pincher grasp (4)
- Highly skilled, dextrous movement
- Individual control of digits
- Coordinated
- Requires primary motor cortex
432
Describe the power grasp (4)
- Strong, but unskilled
- Low dexterity
- Fingers move together
- Persists with damage to primary motor cortex
433
Many primary cortex neurons are selective to...
A particular direction of movement
434
Some primary motor cortex neurons project directly to...
Alpha motor neurons (direct control of activating a muscle)
435
What is the firing of some motor cortex neurons correlated with?
The distance of a movement, others encode the speed of movement
436
What 2 brain areas are involved in the modulation of movement?
1. Basal ganglia
2. Cerebellum
437
Where is the basal ganglia found, and what role does it play? What diseases is it implicated in?
- Found underneath the cortex, overtop the thalamus
- Plays a role in movement force (amplitude) and direction, and modulates patterns of activity generated in other cortical regions. Also guides memory-influenced behaviours.
- Implicated in Parkinson's and Huntington's diseases
438
What does the cerebellum play a role in?
Movement skill (plays a role in timing and coordination, especially with rapid skilled movements/learned motor responses)
- Critical for acquiring and maintaining motor skills (music, sports, etc)
439
What 5 parts make up the basal ganglia?
1. Caudate nuclei
2. Putamen
3. Globus Pallidus
4. Substantia Nigra
5. Subthalamic nuclei
440
Describe the connections to and from the basal ganglia (3)
- Input from all areas of the cortex and limbic system
- Input from substantia nigra
- Projects back to these areas
441
What is a hyperkinetic (fast movement) movement disorder involving the basal ganglia?
Huntington's disease
442
Damage to which parts of the basal ganglia cause Huntington's disease? What is the origin of this disease?
Damage to caudate and putamen nuclei
Genetic origin: trinucleotide repeat
443
What does Huntington's disease lead to?
Unwanted choreiform movements:
- Involuntary exaggerated movements
- Jerking, writihing and twitching
444
What is a hypokinetic (slow/reduced movement) movement disorder involving the basal ganglia?
Parkinson's disease
445
What causes Parkinson's disease? (2)
- Loss of dopaminergic cells in the substantia nigra
- Decreased input to caudate and putamen
446
What does Parkinson's disease cause? (2)
- Inability to produce normal movements
- Hard to initiate movements
447
What are two treatments for Parkinson's disease?
1. L-DOPA
2. Deep Brain Stimulation
448
What are three specialized regions of the cerebellum?
1. Flocculus
2. Medial
3. Lateral
449
What is the Floccus (Flocculonodular/Floccular lobe) responsible for in the cerebellum?
Balance and eye movements
450
What is the lateral part of the cerebellum responsible for?
Regulates cortical areas for movements of limbs, hands, feet and digits
451
What is the medial part of the cerebellum responsible for?
Face and midline movements
452
Describe what would happen if the medial (midline) cerebellum was damaged (2)
1. Deficits in balance, eye movements, upright posture, and walking
2. Reaching abilities fine (if lateral part is undamaged)
453
What would happen if the lateral cerebellum was damaged?
Decomposition of movements
454
How does the cerebellum actually adjust coordination?
The cerebellum monitors 2 versions of the action:
1. What you wanted to do
2. What you actually did
And calculates the error to let the cortex know how to adjust
455
What is seen in people with cerebellum damage?
They don't make adjustments to movements to maintain accuracy
e.g. control throws dart at target. they where prisms that divert gaze and still improve accuracy while wearing them. When prisms are removed, improve initial accuracy again over time. This is not seen in those with cerebellum damage
456
What is muscular dystrophy, and one specific type (and its cause)?
Muscle wasting
Duchenne's: X-linked trait, onset between 4-6 years
457
Describe Myasthenia Gravis (4)
- Autoimmune disease
- Attach of ACh receptors, causes weaker stimulation by ACh (lower receptor capacity)
- Causes muscle weakness: Head and face first (droopy eyelids), speech and breathing later
- Treat with immune system suppressors (trade-off when you get sick though because the immune system can't fight off pathogens)
458
Describe Amyloid Lateral Sclerosis (ALS), aka Lou Gehrig's disease (3)
- Destroys motor neurons in spinal cord and brain stem
- Muscles waste away without input (atrophy)
- Cause unknown (10% hereditary. Aging, toxins, virus, autoimmune, endocrine).
459
Describe Acute Flaccid Paralysis (AFP) aka Polio-like paralysis aka Guillain-Barré syndrome (4)
- Various (potential) cause(s)
- Affects mainly lower motorneurons
- Reflexes absent and muscles waste
- No specific treatment
460
What are 4 approaches to repairing AFP?
1. Stem cells
2. Central glial bridge
3. Neurotrophins (support neurons)
4. Peripheral nerve bridge (connects neurons)
461
Following loss of function (injury, stroke), what are two ways we can help recovery?
1. Constraint induced movement therapy
2. Brain computer interface
462
Describe constraint induced movement therapy (3)
- Strengthen existing pathways
- Enhance cortex
- Depends on type of injury
463
Describe brain computer interface
Record brain activity, control muscles or exoskeleton (computer recognizes brain activity; e.g. when person wants to move their arm, computer moves mechanical arm)
464
Humans spend about __ of our lives asleep
1/3
465
Define "wake"
A complex state that includes a wide variety of behaviours (eating, drinking, thinking, exercising, sex)
466
Define "sleep"
Often thought of as "not wake", is also a complex state with many distinct parts (resting, napping, deep sleep, snoring, dreaming, sleepwalking)
467
True or false: sleep trends are highly variable and change throughout your life
True
468
Typically, sleep quality and quantity (increase/decrease) as you age
Decrease
469
The average adult should get between ____ hours of sleep
7-8
- But some get much less or much more
470
What are three ways of measuring sleep?
1. EEG - Electroencephalograph
2.EMG - Electromyograph
3. EOG - Electrooculograph
471
Describe the Electroencephalograph (EEG) (3)
- Cortical electrical activity
- Primary measure of sleep
- Described in terms of frequency and amplitude of brain waves
472
What does the EMG (Electromyograph) measure?
Muscle tone
473
What does the EOG (Electrooculograph) measure?
Eye movements
474
What brain wave is characteristic of deep sleep (and what frequency is this?)
Delta (0.5-4 Hz)
475
What brain wave is characteristic of meditation and creativity (and what frequency is this?)
Theta (4-8 Hz)
476
What brain wave is characteristic of relaxed reflection/wakefulness (eyes closed)
- What is the frequency and voltage/amplitude?
Alpha (8-13 Hz)
- Amplitude is a little higher than beta waves
477
What brain wave is characteristic of problem-solving/awake mentally
- What is the frequency and voltage/amplitude?
Beta (14-30 Hz)
= Low voltage (amplitude)
478
What brain wave is characteristic of heightened awareness (and what frequency is this?)
Gamma (35+ Hz)
479
What are the 2 main divisions of sleep?
1. Slow-wave sleep (SWS), aka Non-REM sleep, N-sleep
2. Paradoxical sleep (aka REM sleep, R-sleep)
480
Describe Slow Wave sleep (SWS)/Non-REM sleep/N-sleep (2)
- amplitude, frequency, stages
- EEG activity has increasing amplitude and decreasing frequency
- 3 (4) stages - progressive changes in EEG
481
How do stages 3-4 of SWS differ from the other two stages
Waves have a higher amplitude and lower frequency
482
Describe paradoxical sleep/REM sleep/R-sleep (5)
- Dreaming/nightmares
- Wake-like EEG
- Low amplitude, high frequency
- Rapid saccadic eye movements (REMs)
- Muscle atonia (reduced muscle tone) : antigravity muscles shut off (some muscle movements: eye muscles, muscles in the middle ear, diaphragm, some twitching in postural muscles)
483
All non-REM sleep is characterized by... (3)
- Some muscle tone/activity
- Slow rolling eye movements
- Drop in body temperature, heart rate, breathing
484
Non-REM sleep progresses from ____ to _____
Low amplitude/high frequency to high amplitude/low frequency
485
Describe stage N1 of non-REM sleep (3)
- Transition from wake into sleep
- Lasts several minutes
- Low amplitude, mixed frequency (includes 4-7 Hz Theta)
486
Describe Stage N2 of non-REM sleep (3)
- EEG gets a little slow and higher amplitude
Also shows:
- Sleep spindles (11-16 Hz, high frequency)
- K complexes (very high amplitude)
487
Describe stages N3/4 of non-REM sleep (4)
- Deep sleep
- Slow wave sleep (in humans)
- High amplitude, low frequency (0.5-2 Hz, delta waves)
- Little dreaming, lack of content, more like vague images
488
The 1st half of the night is predominated by ____, while the last half is predominated by _____
Slow wave sleep (little REM), REM (little or no stage 3/4)
489
Drift between slow wave and REM happens in about...
A 90 minute cycle
490
What is the order of time spent in each sleep stage (from most to least)
2>5 (REM) >4>3>1
491
What stage of sleep do night terrors (parasomnia, type of arousal disorder) occur during?
Slow wave sleep (N3)
492
What happens to dreams as the night progresses?
They become more frequent and longer
493
Why can't we remember dreams?
Part of memory function (encoding) in impaired during REM, so dreams are difficult to remember the next day
- anything that occurs during sleep is hard to remember
494
Why do we dream?
Not really known. Could be random activity, or to protect the cortex.
495
What is rebound sleep?
Due to sleep deprivation, increase of sleep above normal levels (REM rebound if you miss out on REM one night, get lots the next night)
- Stage-specific
496
What are three consequences of sleep deprivation?
1. Irritability
2. Decreased concentration/attention
3. Can accumulate a debt if you get less than ~7 hours of sleep a night
497
What are 4 reasons why we sleep?
1. Energy conservation
2. Food source/caloric content
3. Sleep as a restorative process
4. Memory storage (consolidation)
498
Describe how sleep may help with energy conservation (3)
- Inactivity
- Low brain activity during NREM, saves energy
- Body temperature drops
499
Describe how sleep may help with food source/caloric content (2)
- Predator-prey relation (prey stay awake more to avoid danger, while predators can afford to sleep more)
- REM as periodic vigilance
500
True or false: herbivores sleep less while carnivores sleep more
True; herbivores need to spend time grazing and be alert for predators, while carnivores sleep more
501
Describe uni-hemispheric slow-wave sleep (asymmetric slow-wave sleep) (4)
- One half of the brain is in deep sleep (the eye corresponding to this half is closed while the other eye remains open)
- EEG shows slow-wave sleep in one side; the other side shows a characteristic tracing of wakefulness.
- Observed in a number of terrestrial, aquatic and avian species
- Suggests that sleep is necessary and serves some essential function
502
Describe how sleep serves as a restorative process (2)
- Rest helps physical fatigue, while sleep is necessary to relieve mental fatigue
- Growth hormone released at night (restorative)
503
What is the world record for going without sleep?
11 days
504
What happens if you lose sleep?
- Little effect on person (physiologically)
- Slow-wave sleep is made up first, followed by a rebound in REM
- Sleep deprivation leads to increased infection (immune system impacted) and death in rats
505
What does total sleep loss cause to rats?
- Rats will die in about 4 weeks without sleep
- Metabolism gets totally messed up (circadian rhythms)
506
How has sleep been shown to help with memory consolidation (training and testing example)?
Theory: sleep facilitates the storage of memories
Test:
- Group A: Train in AM, and test in PM and PM
- Group B: Train is AM, and test in PM and AM (did better after sleep)
- Group C: Train in PM and test in AM and PM (did better after sleep)
507
Other than better test results in the morning, what are 3 other pieces of evidence for sleep's role in memory storage?
1. During REM, circuits become activated that were active during training
2. Birds learning a new song will show activation in auditory areas during REM sleep
3. Sleep deprivation decreases performance on learned tasks
508
How is sleep regulated in general?
Homeostatic drive:
- Possibly hormonal signals: increases in adenosine during the day and melatonin during the night
- Adenosine doesn't cause sleep, but facilitates it
And circadian drive
509
Describe how the brain controls wake using ACh
Acetylcholine from the brainstem Reticular Activating System (RAS) and basal forebrain are important for wake
- RAS stimulation leads to wake-like EEG
510
What does a RAS lesion result in?
Persistent coma (since it is involved in released ACh needed for wake)
511
Activation of which 3 brain parts (and their associated hormones) by the RAS results in feeling wake (and are all active during wake)? How do these project?
1. Raphe nuclei (releases 5-HT)
2. Locus coeruleus (releases NE)
3. Tuberomammilary Nucleus of the hypothalamus (releases HA, remember that first generation anti-HA makes you drowsy)
All project widely in the cortex and communicate with each other
512
What happens to the Raphe nuclei, Locus coeruleus and Tuberomammilary Nucleus during REM sleep?
These areas are silent (antidepressents suppress REM sleep)
513
What is hypocretin (orexin), where is it released from and how does it project?
A neuropeptide released from the dorsolateral hypothalamus
- Orexin neurons project to many of the wake centers and activates them
- Projects also to the cortex, promoting arousal
514
What happens if the brain cells that produce hypocretin (orexin) die?
Type 1 narcolepsy
- The sleep/wake and REM system become dysregulated
- One of the symptoms is cataplexy (muscle weakness/paralysis)
515
What is the role of the Ventrolateral Preoptic Area of the hypothalamus (VLPO) in sleep?
Releases GABA, which inhibits the activity of wake promoting regions:
- Tuberomammilary Raphe
- Locus coerulus
- RAS
This leads to sleep
516
What is the role of melatonin in sleep, and where is it secreted from?
"Sleep" hormone, derived from serotonin
- Secreted by the pineal gland
- Highest levels during the night
517
Sleep and wake mutually oppose each other. How are transitions between the two states regulated?
By a flip-flop model. Your circadian clock (SCN) contributes by reinforcing the right state at the right time
Homeostatic drive also contributes:
- Adenosine
- Melatonin
- Orexin
518
Biological clocks ____ rhythmic changes in the environment
Anticipate
- do not respond
519
Biological clocks are a ____ organization of _____
Temporal, behaviour
- helps avoid predators and competitors
520
What are biological rhythms? What are they related to?
Rhythmic (e.g. daily, seasonal) changes in physiology and behaviour
Related to:
- Earth's rotation about its axis (tilt of axis, axial rotation, and orbit)
- Earth's progression around the sun
521
What are the 4 main classes of biological rhythms?
1. Circannual
2. Infradian
3. Circadian
4. Ultradian
522
Circannual rhythms occur...
- Provide an example
Every year (e.g. migratory cycles of birds)
523
Infradian rhythms occur...
- Provide an example
Longer than 24 hours but shorter than one year (e.g. human menstrual cycle)
524
Circadian rhythms occur...
- Provide an example
~Daily (e.g. human sleep cycle)
525
Ultradian rhythms occur...
- Provide an example
Less than 24 hours (e.g. human eating cycles)
526
True or false: we've only very recently started to understand how circadian rhythms work
True
527
How are rhythms typically studied?
Studying animals, often locomotor activity (a running wheel connected to computer)
- ACTOGRAM detects activity levels
But can use other measures as well: other behaviours, e.g. feeding, grooming, perch hopping birds
- physiological measures
528
What are actograms?
A visual representation of an organism's activity during the day/night and over many successive days
- Can use an actogram to monitor changes over time under constant conditions
529
In the absence of environmental cues, an organism's activity seen on an actogram is referred to as...
Free-running
- The behaviour is endogenous (has an internal origin) if the behaviour continues to show every day independently of its external environment
530
Why is the circadian sleep clock "sloppy"?
Permits it to track changing dawn/dusk
531
Human biology is most closely ties to ____ variations, rather than ____
Daily, seasonal cycles
532
True or false: Circadian rhythm is more than activity/rest
True; pulse, blood pressure, body temperature, cell division, blood cell count, receptor density, gene expression protein synthesis, etc.
533
What are two examples of physiological parameters that impact human circadian rhythms?
1. Hormones (e.g. cortisol, melatonin)
2. Body temperature
534
What are two examples of psychological parameters that impact human circadian rhythms?
1. Alertness
2. Reaction time
535
True or false: Even though our circadian clock runs a little slow (<24 hours), under normal conditions we exhibit 24h patterns in behaviour and physiology
- What does this mean for our clock?
True; our clock needs to be reset each day
536
What are 6 examples of cues that reset the circadian clock?
1. Sunrise/sunset
2. Social interaction
3. Exercise
4. Food
5. Stress
6. Ambient temperature
537
What is a Zeitgeber?
An environmental cue that gives information about time
538
What do Zeitgebers synchronize?
The circadian clock through entrainment (alignment of the internal biological clock to external time cues)
539
What is the most potent zeitgeber?
Light
540
What happens to rhythms in "time-free" environments? What can reset the circadian clock?
"Free-running" rhythm, short light pulse can reset the circadian clock
541
What is Edison's curse, and what has it led to?
The light bulb has allowed people to be active at times of the day when we normally wouldn't be
- Shift workers working at times when the body would normally be sleeping
- Rotating shift workers constantly jumping to new shifts
Increases the rate of on the job accidents and disease
542
What is known as the master circadian clock?
The suprachiasmatic nucleus (SCN) located in the hypothalamus
543
What is unique about SCN, and what does this suggest?
Single isolated SCN neurons are rhythmic on their own (don't get signals from other neurons)
- Suggests that the clock rhythm is intrinsically regulated
544
What happens if the SCN in animals is lesioned? What about when the SCN is transplanted?
When the SCN is lesioned, animals become arrhythmic. When the SCN is transplanted, animals show normal rhythm
545
What is the input to the SCN?
Special photosensitive retinal ganglion (ipRGC) which contains melanopsin that are sensitive to bluish light but also get input from classic photoreceptors
- Cover a wide area of the retina
546
Describe how the SCN acts as a pacemaker
The SCN may not drive behaviours directly
- SCN-lesioned animals still eat, drink and sleep, they just do it haphazardly
- The SCN is controlled by light. The SCN controls rhythms in "slave" oscillators that target other structures. These targets regulate the behaviour.
547
Where are "slave oscillators" found?
Other areas in the brain and in the periphery
548
Describe how the SCN cells regulate their own activity levels
Transcription-translation negative feedback loop
- Interplay of several genes (PER, CRY, CLOCK, BMAL) within SCN neurons
1. A gene is activated
2. mRNA is produced
3. Protein being produced
4. The protein feeds back into the nucleus and turns off its own transcription
Takes about 24 hours
549
What genes are most associated with the circadian rhythm? Mutations in which of these genes have been associated with human sleep disorders?
Three "period" genes: period 1, 2, 3
Mutations in period 2 and 3 have been associated with human sleep disorders
550
What are mutations in the period 2 protein associated with?
Advance sleep syndrome (sleep very early and wake up very early)
551
What are mutations in period 3 protein associated with?
Delayed sleep phase disorder (DSPD; "night owls")
552
Mutations in the CRY1 protein are associated with...
Delayed sleep phase disorder
553
Mice trained in the day (lights on) acquired (better/worse) fear conditioning than mice trained at night (lights off)
- What was this independent of?
Better
Independent of the animals' L/D cycle
554
How is melatonin related to learning and memory?
Melatonin inhibits long-term potentiation (LTP) in the hippocampus; LTP is thought to be essential in the formation of memories
555
Define neuroplasticity
The nervous system's potential for physical and/or chemical change, which enhances its adaptability
556
What are 5 experiences that change the brain (i.e. impact neuroplasticity)?
- What is common to these experiences?
1. Development
2. Culture
3. Preferences
4. Coping
5. Learning
Learning is common to these experiences
557
Define learning
A change in an organism's behaviour is a result of experience
558
Define memory
The ability to recall and/or recognize previous experiences
559
What is a memory trace? What does it correspond to?
A mental representation of a previous experience
- Corresponds to a physical change in the brain, most likely involving synapses and ion channels
560
How are memory and age associated?
Performance declines with age for speed of processing, working memory and long-term memory (but word knowledge is preserved)
561
Define reflex
Unlearned, automatic response by an organism to a stimulus in the environment
562
What is non-associative learning?
Changes in behaviour toward a stimulus in the absence of any apparent associated stimulus or event (habituation and sensitization; e.g. noise)
563
What are the two types of behavioural learning?
1. Associative learning
2. Social learning
564
What is associative learning?
Form of learning that involves connecting certain stimuli or events that occur together in the environment (classical and operant conditioning)
565
What is social learning?
New behaviours can be acquired by observing and imitating others (observational learning)
566
What is the theory of behaviour learning in general?
Theory that behaviour can be changed or learned through reinforcement, either positive or negative, by the introduction of a stimulus
567
What are the three major types of behavioural learning?
1. Classical conditioning (aka Pavlovian conditioning)
- Learning through association
2. Operant conditioning
- Learning through consequence
3. Observational learning
- Learning through observation
568
What is the unconditioned stimulus (UCS) in classical conditioning?
A stimulus that unconditionally - naturally and automatically - triggers an unconditioned response (UCR)
569
What is the unconditioned response (UCR) in classical conditioning?
The unlearned, naturally occurring response to the unconditioned stimulus, such as salivation when food is in the mouth
570
What is the conditioned stimulus (CS) in classical conditioning?
An originally neutral stimulus that triggers a conditioned response (CR) after association with an unconditioned stimulus
571
What is the conditioned response (CR) in classical conditioning
The learned response to a formerly neutral conditioned stimulus
572
What is classical conditioning, and who first described it? What are the 3 stages of classical conditioning?
Learning through association
- First described by Pavlov
3 stages: Before, during, after
573
Who were the first psychologists to apply classical conditioning to human behaviour? What phenomenon does this explain?
Watson and Rayner
Explains the development of phobias
574
What is operant conditioning and what is it also known as?
Learning through consequence
Instrumental conditioning
575
What did Edward Thorndike and BF Skinner say?
Learning procedure in which the consequences (such as obtaining a reward) of a particular behaviour (such as pressing a bar) increase or decrease the probability of the behaviour occurring again
576
Describe Thorndike's puzzle box and Skinner's box
Thorndike's puzzle box: The cat is placed in the box with the food reward outside. The hungry cat eventually learns that pressing on the lever will result in getting out of the box and getting to the food
Skinner's box: Rat in box received food through dispenser if they press the lever
- First time action is done is through consequence
577
What is observational learning, and the 4 stages/requirements of it?
The acquisition and later performance of behaviours demonstrated by others
4 stages:
1. Attention
2. Retention
3. Production processes
4. Motivation
578
Describe the attention stage of observational learning
Extent to which we focus on others' behaviours
579
Describe the retention stage of observational learning
Our ability to retain a representation of other's behaviour in memory
580
Describe the production processes stage of observational learning
Our ability to perform the actions we observe
581
Describe the motivation stage of observational learning
Our need for the actions we witness; their usefulness to us
582
What are the three types of memory?
1. Explicit memory
2. Implicit memory
3. Emotional memory
583
What are the three stages of memory?
1. Sensory memory
2. Short-term memory (working memory)
3. Long-term memory
584
What are the three processes of memory?
1. Encoding
2. Storage
3. Retrieval
585
What is implicit memory (and what is it also known as)?
Aka the unconscious/non-declarative memory
Knowledge such as a skill, conditioned response, or recalling events on prompting, but cannot consciously retrieve the information
586
What 3 types of memory make up implicit memory? What additional process also makes up implicit memory?
1. Procedural memory
2. Associative memory
3. Non-associative memory
4. Priming
587
What is procedural memory (a type of implicit memory)?
Involves part of memory that participates in recalling motor and executive skills that are necessary to perform a task (e.g. riding a bike)
588
What is priming?
Exposure to certain stimuli influences the response given to stimuli presented later
589
What is especially important in forming implicit memories?
REM sleep
590
What is explicit memory (and what is it also known as)?
aka Conscious/declarative memory
Intentional recollection of factual information, previous experiences, and concepts
591
Explicit memory is made up of which two types of memory?
1. Episodic
2. Semantic
592
What is episodic memory (type of explicit memory)?
Personal firsthand experiences; events
593
What is semantic memory (type of explicit memory)?
Fact, concepts
594
What is especially important in forming explicit memory?
NREM sleep
595
What is emotional memory?
Memory for events that evoke an emotional response (memory for the affective properties of stimuli or events)
- Can be implicit or explicit
- Re-experience the original emotions engendered by an event
- We tend to remember emotionally arousing experiences vividly
596
Describe the Atkinson-Shiffrin memory model (3 steps)
1. Environmental stimuli is brought into sensory memory (retention 25-2000 ms; large capacity)
- unattaended information is lost
2. Selected attention is brought into working memory (retention 15-30s; capacity is limited)
- unrehearsed information is lost
3. Rehearsed info is encoded into long-term memory (infinite retention period and capacity)
- Some information is forgotten over time (decay or retrieval failure)
597
What is the retention time and capacity of sensory memory?
Retention: 25-2000 ms
Capacity: large
598
What is the retention time and capacity of working memory?
Retention: 15-30 s
Capacity: Limited (7+2 novel units)
599
What is the retention time and capacity of long-term memory?
Retention: Infinite
Capacity: Infinite
600
What is short-term memory, what is it also known as, and what parts of the brain does it involve?
Working memory; few seconds. Information is held in memory only briefly, then discarded
- Involves the frontal lobes
601
What is long-term memory, what is it also known as, and what part of the brain does it involve?
LTM; indefinite duration
Information is indefinite, perhaps for a lifetime;
- Involves the temporal lobe
602
True or false: no single place in the nervous system can be identified as THE location of memory formation
True
603
Which brain part appears to participate in many forms of short-term memory?
Frontal lobe
604
All sensory systems project to the ____
Frontal lobes
605
What is the prefrontal cortex central to in terms of memory?
Central to maintaining temporary (short-term) explicit memories as well as memory for the recency (chronological order) of explicit events
606
How is implicit (unconscious) information processed?
In a bottom-up manner
- Information is encoded in the same way it was perceived
- Passive role of person (not consciously trying to remember something)
- Unidirectional (one-way) bottom-up flow of implicit information. Starts, with inputs from the sensory and motor systems (not considered part of the memory circuit)
607
How is implicit memory thought to be mediated?
Thought to be mediated by a circuit separate from limbic structures (thus no involvement of the hypothalamus, hippocampus and amygdala)
608
How is the basal ganglia involved in implicit memory?
Basal ganglia receive input from the entire neocortex and send projections first to the ventral thalamus from there to the premotor cortex
- The basal ganglia also receive widely and densely distributed projections from dopamine-producing cells in the substantia nigra
609
True or false: Parkinson's patients often have implicit memory failures, while explicit memory function is okay
True; dopamine appears necessary for basal ganglia circuits to function and may indirectly participate in implicit memory formation
610
How is explicit information processed?
In a top-down, or conceptually drive, manner
- Information is reorganized before it is encoded
- Active role of the person
611
Describe the reciprocal connection for explicit memory
The reciprocal circuit: the neocortex projects to the entorhinal cortex (temporal lobe structures), which projects back to the neocortex
- signals from the medial temporal regions to the cortical sensory regions keep the sensory experience alive in the brain: the neural record outlasts the actual experience
- Pathway back to the neocortex means it is kept informed of the information being processed in medial temporal regions
612
What are the 3 primary structures involved in explicit memory?
1. Medial temporal region
2. Frontal cortex
3. Reciprocal connections between those areas
613
What 5 regions of the medial temporal region are involved in explicit memory?
1. Hippocampus
2. Amygdala
3. Entorhinal cortex
4. Parahippocampal cortex
5. Perirhinal cortex
614
What is the parahippocampal cortex involved in for explicit memory? (2)
- Receives connections from the parietal cortex
- Believed to take part in visuospatial processing
615
What is the perirhinal cortex involved in for explicit memory? (2)
- Receives connections from the visual regions of the ventral stream
- Believed to take part in visual object memory
616
What is the entorhinal cortex involved in for explicit memory? (2)
- Receives projections from the neocortex, (para-)hippocampal and perirhinal cortices
- Integrative function: first area to show cell death in Alzheimer's disease
617
What part of the brain consolidates (stabilizes) new explicit memories?
The hippocampus
618
To consolidate a memory trace after learning, memories move from...
The hippocampus to diffuse regions in the neocortex
619
True or false: once memories move from the hippocampus to diffuse regions in the neocortex (during memory consolidation), hippocampal involvement is no longer needed
True
620
What is visuospatial memory?
Using visual information to recall an object's 3D shape and location
621
What does selective hippocampal injury cause? Describe what is seen in monkeys with hippocampal and perirhinal lesions
Severe deficits in various forms of spatial memory
- Monkeys with hippocampal lesions have difficulty learning the location of objects
- Monkeys with perirhinal lesions are impaired in the visual recognition task
622
What is seen in the hippocampus of London taxi drivers and food-storing birds/rodents?
The posterior region of the hippocampus in London taxi drivers is significantly larger than the same region in the control participants (before GPS, since they had to have a spatial memory of the map of London)
The hippocampal formation in food-storing birds and rodents is larger than that of birds and rodents that do not store food.
623
What is reconsolidation?
Restabilizing a memory trace after the memory is revisited
- Whenever a memory is replayed in the mind, it is open to further consolidation
- New information is constantly being integrated into existing memory networks
624
Is it possible to erase negative memories? If so, how?
Yes, by using amnesic agents when the memory is revisited (e.g. in PTSD)
625
What part of the brain is critical for emotional memory? How is this stimulated, and what does it have close connections with? What does it modulate?
The amygdala
- Stimulated by emotionally driven neurochemical and hormonal activating systems (probably cholinergic and noradrenergic)
- the amygdala has close connections with the medial temporal cortical structures as well as with the rest of the cortex
- It modulates the emotional memory circuits in the rest of the brain, especially in the medial temporal and prefrontal regions and in the basal ganglia
626
How does damage to the amygdala affect the memory?
It abolishes emotional memory but has little effect on implicit or explicit memory
627
What are the 6 proposed brain areas involved in emotional memory?
1. AMYGDALA
2. MEDIAL TEMPORAL CORTEX (EXPLICIT MEMORY)
3. Brainstem
4. Hypothalamus
5. Periaqueductal gray (PAG) matter (pain)
6. BASAL GANGLIA (IMPLICIT MEMORY)
628
What processes are essential for long-term memory formation?
Physical changes
- This involves gene expression and protein synthesis
- Physical remodeling (e.g. more synapses, or more receptors)
629
What does strengthening (or weakening) of connections in the brain create in terms of long-term memory?
Creates network that together encodes a memory
- Repeated memory recall, the stronger its neural network
- Consistent recall causes memory to be encoded in other brain areas
630
Describe how the physical representation of memory is an engram
The ensemble of neurons across multiple brain regions manifesting learning-induced changes
- A neuron and its synapses can be involved in multiple engrams (networks)
631
At the neural level, memory is associated with changes that take place at... (2)
- Synapses (synaptic plasticity)
- Ion channels (non-synaptic plasticity)
632
What are 3 ways you can find neural correlates of memory?
1. Determine how synaptic/ion channel changes are correlated with memory in the (mammalian) brain
2. Localize the synaptic/ion channel changes to specific neurons and/or neural pathways
3. Analyze the nature of these changes
633
Describe synaptic plasticity (3)
- Not just the number of connections, but the nature of the connections can change
- Terminal changes
- Dendritic spine changes
634
Pre-synaptic plasticity is (short-term/long-term)
Short-term
635
What are the two types of pre-synaptic (short-term) plasticity?
1. Pre-synaptic inhibition (e.g. habituation)
2. Pre-synaptic facilitation (e.g. sensitization)
636
What is long-term potentiation (LTP)?
Persistent increase in synaptic strength following high-frequency stimulation of a pre-synaptic neuron
- Increased EPSP amplitude over time
- Is thought to play a part in associative learning and memory formation (never proven, but lots of evidence)
637
How long does LTP last?
Can last for hours to days or longer
638
Who first described LTP? Who first recorded LTP in a hippocampus?
First described by Eric Kandel
First described in a hippocampus by Bliss and Lømø
639
What 4 things could the increased EPSP amplitude in LTP be caused by?
1. More neurotransmitter release (pre-synaptic modulation)
2. More sensitive receptors (post-synaptic modulation)
3. More receptors (post-synaptic modulation)
4. Larger synapses (pre- and post-synaptic changes
640
What is long-term depression (LTD)? How does it maintain neural homeostasis
Decrease in EPSP size over time
- One of the several processes to weaken specific synapses in order to make constructive use of synaptic strengthening caused by LTP
- Neurons need to maintain a variable range of neuronal output (if you get strengthening of one synapse (LTP), may need to decrease strength of another synapse to maintain balance
641
What class of chemicals is implicated in LTD?
Endocannabinoids
642
How can the influx of Ca2+ through NMDA receptors impact plasticity?
Ca2+ can trigger changes in gene expression (activates cAMP and CREB)
- CREB binds to DNA and promotes gene expression, which leads to new proteins: new receptors, new synapses, rewiring, longer term plasticity (learning)
643
What is forgetting in general, and what is it suggested to be a result of?
Forgetting is an active process, where connections at the synapse are proactively destroyed
- It is suggested that removal of AMPA receptors is involved
Forgetting is not a failure of memory, but a function of it
644
How do GABA levels impact forgetting?
High GABA levels enhances suppression in the hippocampus: more "forgetting"
645
How is plasticity related to enriched experience? Use rats as an example
Raising rats in enriched enclosures is associated with increased brain weight, more astrocytes, more blood capillaries, more synapses per neuron and increased mitochondrial volume (marker of greater metabolic activity)
- Enriched experience is very important for humans as well
646
What did Scheibel and colleagues discover?
Studied the relationship between the complexity of dendritic branching and the nature of the computational tasks performed by a brain area
Found that life experience alters dendritic morphology
- e.g. career word processors (continuously working with their fingers) have greater differences between finger and trunk neurons than do salespersons
647
True or false: neurogenesis occurs in the mammalian brain
True; while the predominant view prior to the mid 1990s was that there was no neurogenesis, there is evidence that neurogenesis does occur in the mammalian brain (olfactory bulb, hippocampal formation, and possibly neocortex)
- Reason for neurogenesis is still unclear, but can actually weaken existing memories (rewiring existing connections makes it harder to access memories)
648
How do high levels of estrogen impact plasticity?
High levels of estrogen cause more dendritic spines (i.e. synaptic connections) in the hippocampus
649
How do low levels of estrogen impact plasticity?
Low levels of estrogen cause more dendritic spines in the neocortex, but fewer in the hippocampus
- May be related to decline in middle-aged women (due to menopause)?
650
How do glucocorticoids impact plasticity?
Steady levels of glucocorticoids that are seen with prolonged stress may be neurotoxic (glucocorticoids can kill hippocampal cells)
651
How do psychoactive drugs impact plasticity?
Drug-induced behavioural sensitization: escalating behavioral response to the repeated administration of a psychomotor stimulant (e.g. amphetamine, cocaine, or nicotine)
- Sensitization is associated with an increased number of receptors, synapses and dendrites
- These changes were localized to regions (e.g. prefrontal cortex, nucleus accumbens) that receive a large dopamine projection
652
True or false: all nervous systems are plastic in the same general way
True
653
True or false: plastic changes are age-specific
True; brain becomes less plastic as you age
654
True or false: Prenatal events can influence brain plasticity throughout life
True
655
True or false: plastic changes are brain-region dependent
True
656
What is metaplasticity?
The idea that experience-dependent changes interact
657
True or false: plasticity has pros and cons
True
NEUR 321
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