1
Q
Is there a hierarchical organization to the sensory system?
A
- yes
- > primary to secondary to association
Primary
->receives input from thalamus
Secondary
->receives input from primary
Association
- > receives input from more than one primary sensory system
- > mostly receives from secondary
2
Q
How does damage work in the hierarchical sensory system
A
Lower hierarchical levels damaged=loss of function
Higher levels=specific sensory deficits
3
Q
Is agnosia a perception problem or a sensation one
A
-it is a perception problem
4
Q
Describe the functional segregation theory to sensory systems hierarchical organization
A
- they are segregated
- >different analysis within each level
5
Q
Describe the parallel processing theory to sensory systems hierarchical organization
A
- different levels of sensory hierarchy are not just in a series
- > there are parallel system and multiple pathways
6
Q
What are the two types of parallel streams in parallel processing of sensory systems
A
- there is the stream that influence behavior without conscious awareness
- there is the other stream that influence behavior without engaging in conscious awareness
7
Q
What is the claustrum?Where is it in the seonsory hierarchy
A
-it is a thin sheet of neurons under the neocortex
- sits at the top of the sensory hierarchy
- > receives signals from all lower areas to form perception
8
Q
What is amplitude frequency and pitch
A
- amplitude means loudness
- frequency means pitch
- complexity means timbre
9
Q
Do pure tones exist?What kind of a wave is it? Is there a close relationship between tone and pitch
A
- they do not exist
- > only lab produced
- sine wave
- close relationship between tone and pitch
- > can’t localize->uncomfortable
10
Q
Where do you find complex waves
A
- it is found in nature
- >always associated with complex patterns and vibrations
11
Q
What is the fourier analysis and how does the auditory system relate to this analysis
A
- it is breaking down the complex waves into component sine waves
- > different frequencies and amplitudes result
12
Q
Describe the movement of vibrations throughout the outer ear
A
- it travels down the auditory canal
- vibrates the tympanic membrane
- > vibration is transferred to the ossicle
- > malleus, anvil, stapes
-note stapes trigger vibrations in the oval window
13
Q
Describes how pressure change in works in the organ of corti
A
-each pressure change in the oval window travels along the organ of corti as a wave
14
Q
What are the 2 membranes of the organ of corti
A
- basilar membrane
- > the hair cells are mounted here
- tectorial membrane which rests on the hair cells
-note round window dissipates vibrations
15
Q
How do different frequencies of sound stimulate the organ of corti in different ways
A
High frequencies
->increase haircells by the oval window
Low frequencies
->increase haircell stimulation by tip of basical membrane
-note different components of complex sounds act in different locations
16
Q
How is the tonotopic of map described
A
- it describes each level of the auditory system
- >the system is organized by frequency
17
Q
What is the endolymph
- > what ion is it rich in?
- > also is there an ion imbalance and if so what maintains this ion imbalance
A
- the endolymph is the fluid surrounding hair cells
- > it is rich in potassium ions
- there is an ionic imbalance
- > the tight junctions maintain this ionic imbalance
18
Q
What are the tip links in cilia hair cells
A
- they are thread like connections from the tip of the cilium to non specific cation channel on the neighbouring cilia
- note cation channels open with movement towards the tallest
- > opens the voltage gated calcium channels once the potassium influx depolarizes the cilia
19
Q
What are the numbers of the outer hair cells like compared to the inner one? Where is it strongly connected to? Are there efferent connections
A
- 3x more numerous than inner ear
- strong connection to tectorial membrane
- input from brain to ear
- > there are efferent connections
- > so top-down
20
Q
Are there multiple networks of auditory pathways
A
- multiple network of auditory pathways
- > different compared to visison
-axons of each auditory nerve synapse on ipsilateral cochlear nuclei
21
Q
Describe movement of signal from superior olives to contralateral and ipsilateral A1
A
- signals from each ear combined
- > go to both sides of olives
- they then project to inferior colliculi via lateral meniscus
- then the MGN and finally A1
22
Q
What is the difference between lateral and medial superior olives. Where do these olives project their signals to?
A
- medial responds to differences in time of arrival
- lateral responds to differences in amplitude or loudness
- they both project to superior colliculi
- > where it is retinotopically organized
23
Q
Where is the auditory cortex located? Is it similar in humans and primative relatives? How does the cortex respond to pure tones as compared to relevant tones?
A
- they are located in temporal lobes within the lateral fissure
- similar in humans and primative relatives
- respond less to pure tones than relevant tones
24
Q
Describe the difference between A2 and A1 auditory cortex
A
A1
- > receives majority of input from mgn
- > organized into functional columns
- tonotopic
A2
- > more complex
- > adjacent to A1
- > organized by frequency
25
Describe the two streams of the A2 cortex
Prefrontal cortex and inferotemporal cortex
- >referred to as the anterior pathway
- >what pathway
- >identify sounds
Posterior parietal cortex
- >posterior auditory pathway
- >here some neurons have visual and others have auditory receptive fields
- >it is the where pathway
- >locates the sounds
- >prepares for action
26
Is auditory cortex damage rare?
- it is rare
| - >if it does occur it is more than just auditory cortex damage
27
What is conductive deafness originate from?
-it originates from the ossicles
28
What is nerve deafness? Where does it originate from?
- it can be due to loss of hair cell receptors
- >frequency specific
- >it is a characteristic of age related deafness
-note it originates from nerve damage
29
What is the main purpose of cochlear implants? How does it work?Does it restore hearing fully
- main purpose is to bypass hair cell damage
- it converts sounds picked up by the microphone to electric signals
- >carried to electrodes which excites the auditory nerve
-it does not restore hearing fully
30
What is tinnitus? What are the cause of it?
-tittinus is the perception of noises in the head or ear which don't have an external source
Due to
- >normal hearing
- >following hearing loss
- >common with aging
31
Does tinnitus continue even after auditory nerve cuts?
- yes
| - >this suggests that tinnitus is a product of central processing
32
Describe the three systems of the somatosensory system
1) Exteroreceptive system
- >senses external stimuli applied to skin
- >mechanical stimuli, thermal stimuli and nociceptive stimuli
2) Proprioceptive system
- >monitors the position of the body
- >receptors from muscles, joints and organs for balance
3) Interoceptive system
- >general info about bodily conditions
- >eg; temperature and blood pressure
33
Describe the characteristics of cutaneous receptors. Note there is 5 of them.
1) embedded in skin
- >stimuli change chemistry of receptor to change ion permeability
2)Not 1 receptor for each sensation
3) Free nerve endings
- >Multimodal where one is for pain and the other is for temperature
4) Pacinian corpuscles
- >mechanoreceptor
- >sense sudden skin displacements
- >adapt rapidly
- >cannot send constant pressure
- >note they are the LARGEST AND THE DEEPEST
5) Merkels disks and Ruffini ending
- mechanoreceptors
- >adapt slowly
- >gradual skin indentation is Merkel
- >gradual skin stretch is Ruffini
34
What are dermatomes? Where do neural fibres from cutaneous receptors enter the spinal cord?
- area of the body that is innervated by left and right dorsal roots of a given segment of the spinal cord
- note nueral fibres from cutaneous receptors enter the spinal cord via dorsal roots
35
How does the destruction of single dorsal root affect somatosensation?
- destruction of single dorsal root produces little somatosensory loss
- >this is due to the overlap between adjacent dermatomes
36
What are the 2 major pathways in which info ascends from each side of the body to the cortex
1) Dorsal column medial lemniscus
- >tends to carry touch and proprioception
2) Anterolateral system
- >tends to carry temperature and pain information
- note there is no perfect separation between the two pathways
- >there is some overlap
37
Describe the dorsal column medial lemniscus pathway
- dorsal root ipsilateral
- >then synapse in dorsal column nuclei
- >then cross over in medulla
- >finally ascends up the medial lemniscus
38
Where do the neurons go after they end up in the medial lemniscus
Ventral posterior thalamus
- >receives input from 3 branches of trigeminal nerve
- >carry this info to the contralateral side of the face
Somatosensory cortex(s1) and somatosensory cortex(s2)
- >most project to s1
- >others bypass s1 and go straight to s2
39
Describe the anterolateral system dorsal root neurons
- they synapse as soon as they enter the spinal cord
- >second order neurons decussate
- >ascend into brain contralaterally
- >others do not decussate and ascend ipsilaterally
40
Do lesions eliminate pain and temperature sensation
-no
41
Describe the three tracts of the antero lateral system
1) Spinothalamic tract
- >projects to ventral posterior thalamus
- >same as dorsal column
2) Spinoreticular tract
- >projects to reticular formation
- >then to parafasicular nuclei and intralaminar nuclei of thalamus
3) Spinotectal tract
- >projects to tectum(colliculi)
42
How does the anterolateral system interact with the thalamic and the somatosensory cortices?
- 3 branches of trigeminal nerve carry pain and temperature info to the ventral posterior thalamus
- >pain and temperature info that reaches the thalamus is then projected onto the s1 and s2
43
What happens to body sensation
- there is no body sensation felt below the level of the cut
| - >lower spinal injuries are better
44
How did penfeild map the primary somatosensory cortex
- different areas of the somatosensory cortex stimulate different parts of the body
- it is organized somatotipically
45
Describe the somatosensory homunculus
- there is contralateral input
- it is distorted
- largest areas are dedicated to parts of the body with the finest tactile discrimination
- >require many neurons with small receptive fields
- >small S1 areas come from the large parts of the body
- >note there are few neurons with large receptive fields
46
Describe the columnar organization in the S1 cortex
- there are antagonistic and excitatory receptive fields
| - >center-surround
47
Describe the columnar composition of the S1 cortex
- there are 4 functional strips in each column
- >each strip for each kind of somatosensory input
- >touch/pressure/heat/pain
- >integration of these parallel streams
48
What happens as you move anterior to posterior in the column composition of the S1 cortex
- there are more specifc/complex responses
| - >this shift from the anterior to the posterior is referred to as hierarchical organization
49
Is S2 also somatotopic? Where does it extend into? Where does it receive most of its input from?Where does the output from s1 and s2 eventually end up in?
- S2 is also somatotopic
- it extends into the lateral fissure
- the output eventually ends up in the posterior parietal lobe
50
Describe the dorsal and ventral processing streams of the somatosensory
Dorsal
- >S1->posterior parietal
- >multisensory integration
- >directs attention
Ventral
- >S1->S2
- >perception of objects by shape
51
Is damage to somatosensory cortex mild? If yes, then please explain why
- it is often mild
| - >because there are numerous parallel pathways in the somatosensory cortex
52
How do bilateral deficits arise in the somatosensory cortex
-they arise due to s1 and s2 lesions
53
What is astereognosia
- it is the inability to recognize objects by touch
- >it is rare
- >it is a somatosensory agnosia
54
What is asomatognosia? Is it unilateral?
- failure to recognize ones own body parts
- usually unilateral
- >usually affects the left side
- >associated with right posterior parietal damage
- note there is contralateral neglect
- >failure to respond to stimuli that are contralateral to the injury
55
Is pain parodoxical
- yes
- >it is adaptive
- >it allows us to survive and avoid potentially harmful stimuli
56
Describe the cortixal representation of pain
- there is clear corticla representation
- >many areas of the cortex are activated
- >varies greatly among individuals
57
Describe the role of s1 and s2 in pain stimuli. Look at slide 51.
- s1 and s2 both respond to painful stimuli
| - >removal of s1 and s2 does not affect pain perception
58
Describe the anterior cingulate cortex relation to pain
- it is the most commonly linked to pain
- PET imaging increases for certain instances of pain within this region
-likely involved in emotional, behaviour adaptations to pain rather than the pain stimuli itself
59
What is prefrontal lobotomy
- it removes the anterior cingulate cortex
- >patients then have no emotional reactions to pain
- >they still feel the pain
60
Describe descending pain control in terms of cognitive and emotional factors
- pain can be suppressed by cognitive and emotional factors
- >eg; wounds suffered by soldiers in battle
- >or injury in life threatening situation where you don't feel the pain until the threat is gone
61
How does the gate control theory of pain describe the ability of the brain to block pain
- when the gate is open
- >signals coming from the spinal cord can be transmitted to the brain
- when the gate is closed
- >descending signals from the brain can block pain coming from the spinal cord
- >so no conscious processing of the brain
62
What is the role of the periaqueductal gray
- it is an analgesic
- >has pain blocking effects
- >contains specialized opiate receptors(Hi opiate receptors)
- stimulate pag and there is no pain
- that is why certain drugs and psychological factors may block pain through the pag descending circuits
63
What is the periaqueductal gray relationship to the endorphins
- it is the site of endorphin production
| - >makes and releases endorphins
64
Describe neuropathic pain.
- it is the bad side of neuroplasticity
- there is severe chronic pain in absence of painful stimuli
- >develops after injury
- >the injury heals but the chronic excruciating pain remains
- pain is triggered by innocuous stimulus
- >light, breeze, or soft touch
65
What is the mechanism of neuropathic pain
Mechanism is unknown
- >pain source is in the cns
- >pain medications are ineffective
66
Describe the purpose of chemical senses
- monitor chemical content in the environment
| - >works together to produce flavour
67
What factors are involved in flavour? Where is all this flavour processed?
- smell and taste act together during the meal
- other factors include:
- >temperature, look satiety and texture
-this is all processed in association areas
68
Describe the role of phermones in animals
1) influence physiology and behaviour
2) Regulate social interactions
3) Sex and aggression within hamsters
- >note once female vulva is removed and cannot release phermones
- >the aggression is stopped
69
How do phermones work in humans? Describe different cases.
- the olfactory system is greatest during ovulation or pregnancy
- you can id genders by breath or sweat in underarms
- males can judge state of cycle by by vaginal odor
- synchronization of menstrual cycles
70
Describe the olfactory system receptors
- receptor cells on upper part of nose
- >receptors embedded in dendrites in nasal passage
- >axons extending from dendrites then travel through cribriform plate
- >this axon then projects to the olfactory bulb
71
Describe the olfactory mucosa
- it is mucus covered tissue
- >receptor of cells are embedded in here
- >organization is unclear
72
What is the cribriform plate
- it is a porous portion of the skull
| - >axons pass through this portion
73
Describe the olfactory receptors and its respond to odours
- each receptor type responds in varying degrees to variety of odors
- all receptors of the same type project to same general location in the olfactory bulb
74
Describe the receptor lifespan in the olfactory system
- new receptors are created regularly
- >they replace deteriorated ones every few weeks
- >unknown how the cell are regulated
75
What are olfactory glomeruli
- they are clusters of neurons
- outside of the olfactory bulb
- receive input from multiple receptor cells
- >all from the same receptor type
76
Is there chemotopuc organization to glomeruli
- yes, symmetry in glomeruli across both bulbs
| - different odors produce different spatial patterns of activity on the bulb
77
What are two major olfactory pathways
- one projects to the limbic system
- >mediates emotional response to odors
- the other goes through medial dorsal nucleus of the thalamus to the orbitofrontal cortex
- >this allows for conscious perception of odors
Psych 275
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