***PSYCH 275- Brain & Behaviour > Chapter 6 - Vision > Flashcards

Chapter 6 - Vision Flashcards

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1
Q

What is sensation?

A

Stimulation of the SENSE organs by PHYSICAL stimuli from the environment

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2
Q

What is perception?

A

SUBJECTIVE selection, organization, and interpretation of that SENSORY input

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3
Q

What is transduction?

A

The process where SENSATIONS are translated to ELECTROCHEMICAL TRANSMISSION

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4
Q

Is perception subjective?

What is Fechners Law?

A

Yes

Even if stimulus intensity changes LINEARLY, our perception of that CHANGE is NOT linear
———————————————————————————-

Fechners law:
- subjective sensation is PROPORTIONAL to the logarithm of the stimulus intensity

Ex) TV at night 5 vs 6
Tv in day 20 vs 25 - doesn’t seem as big now that the magnitude is bigger

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5
Q

What is signal-detection theory?

A

Detection of stimuli involves DECISION PROCESSES as well as SENSORY PROCESSES

Both processes are influenced by a variety of factors besides stimulus intensity

Internal state, experience etc…

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6
Q

What are sensory receptors?

What are 2 different systems?

A

SPECIALIZED cells that transduce SPECIFIC types of SENSORY ENERGY into NEURAL ACTIVITY

Different systems have different receptors that respond to different stimuli…

  1. Vision: photoreceptors transduce light
  2. Gustation: taste cells transduce dissolved chemicals
    Etc…
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7
Q

What are receptive fields? (Sensory receptors)

A

Area in which a STIMULUS modifies a RECEPTORS ACTIVITY

Have to have overlap receptive field

Ex) think of a circle and how a smaller circle overlaps it VS when it doesn’t overlap it. Or if it very much overlaps it (in the middle)

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8
Q

What is receptor density and sensitivity?

A

UNEQUAL distribution of RECEPTORS allows for INCREASED SENSITIVITY in IMPORTANT AREAS

Higher density of receptors gives BETTER resolution

Ex) think peripheral vision, this is why we shift our head to look at something straight on if we think its important

Ex) think back that mosquitoes can bite your hand less easily (we have more receptors there) VS they can bite your legs more easily (we have less receptors there)

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9
Q

What does our sensory pathway include?

A

Sensory receptors —> thalamus (helps route) —> cerebral cortex

***MODIFIED AT VARIOUS STAGES
= ALLOWS INTERACTIONS B/W SYSTEMS

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10
Q

What is sensory coding?

A

Sensory information encoded by ACTION POTENTIALS traveling along PERIPHERAL nerves to the CNS

PRESENCE/INTENSITY of a stimulus can be encoded by an INCREASE/DECREASE in firing rate (rate law)

Ex) ____I____I____I___I___
Baseline firing

Ex) __I_I_I_I_I_I_I__
Increased firing

Ex) ______I_______I_______I_____
Decreased firing

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11
Q

What is the topographic map?

In mammals what do we see?

A

NEURAL-SPATIAL representation of the body or the areas of the sensory world PERCIEVED by a sensory organ

In mammals…
Each sensory system has at least ONE PRIMARY CORTICAL AREA
Project to secondary areas
***specialized

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12
Q

What is the retinotopic map?

A

NEURAL MAP of what is detected at the RETINA projected on the CORTEX

We view things inverted at the back of our eye (our retina)

Points close together on an object and on the retina will activate neurons close together in the brain

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13
Q

What is cortical magnification?

A

Small area of FOVEA is represented by LARGE AREA on VISUAL CORTEX

0.01% : 8-10% on cortex

Why we are good at looking DIRECTLY at things with fine detail

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14
Q

What is light?

A

Form of ELECTROMAGNETIC RADIATION that travels as a WAVE

Visible light ~400-700nm

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15
Q

What are the “properties” of light?

(Amplitude, wavelength & purity)

A

Amplitude: perception of BRIGHTNESS

Wavelength: perception of COLOUR

Purity: mix of wavelengths, perception of SATURATION

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16
Q

Name the 4 main structures of the eye and their function

A
  1. Cornea: clear outer covering
  2. Iris: opens & closes to allow more or less light
    - Pupil: hole in iris
  3. Lens: focuses light
  4. Retina: where light energy initiates neural activity
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17
Q

What happens when light focuses on the retina?

A

Light-sensitive surface at the back of the eye that consists of NEURONS and PHOTORECEPTOR CELLS

TRANSLATES LIGHT —-> ACTION POTENTIALS

Discriminates wavelengths (colours)

Works in wide range of light intensities

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18
Q

What happens when light focuses on the fovea?

A

Region at the CENTER of the retina that is SPECIALIZED for high acuity

Receptive field at the center of the eyes visual field

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19
Q

What is myopia?

A

“Nearsightedness” inability to see DISTANT objects clearly

Imaged is focused in FRONT of retina

Caused by:
- refractive myopia: cornea/lens bends too much light
- axial myopia: eyeball is too long

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20
Q

What is hyperopia?

A

“Farsightedness” inability to see nearby objects clearly

Imaged focused BEHIND retina

Usually caused by eyeball that is too SHORT

Constant accommodation for nearby objects can lead to eyestrain/headaches

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21
Q

What is the blind spot?

A

Includes region of the retina (optic disc) where axons forming the optic nerve leave the eye and where blood vessels enter and leave

Has NO PHOTORECEPTORS

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22
Q

What are rods?

(Photoreceptors)

A

More NUMEROUS than cones

Sensitive to LOW levels of light (dim light)

Mainly used for NIGHT VISION

One type of pigment ONLY

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23
Q

What are cones?

A

Highly responsive to BRIGHT LIGHT

Specialized for COLOUR and HIGH visual acuity

In the FOVEA ONLY

3 types of PIGMENT

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24
Q

What are the 3 types of cone pigments?

A

Range of frequencies…

419nm (blue/short)

531nm (green/middle)

559nm (red/long)

Wavelengths

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25
What are 4 types of retinal neurons?
1. Bipolar cell: - RECIEVES input from photoreceptors 2. Horizontal cell: - LINKS photoereceptors & bipolar cells 3. Amacrine cell: - LINKS bipolar cells & ganglion cells 4. Ganglion cells: (different slide)
26
What are the 2 types of ganglion cells?
1. Magnocellular cell (M-cell): - large - receives input primarily from RODS - sensitive to LIGHT/MOVING stimuli 2. Parvocellular cell (P-cell): - small - receives input primarily from CONES - sensitive to COLOUR
27
What is the optic chiasm?
Visual pathway JUNCTION of the optic nerves from each eye Axons from the nasal (inside) cross over to other side of the brain Axons from the temporal (outer) remain on the same side of the brain ***JUST BEFORE visual info enters the brain
28
What are the 3 different visual pathways (after entering the brain through axons of retinal ganglion cells)?
1. Geniculostriate system: - info to lateral geniculate nucleus (LGN) - primary visual cortex 2. Tectopulvinar system: - info to superior colliculus - tecto and midbrain - info processed in more basic way 3. Retinohypothalamic tract: - smaller pathway to hypothalamus - short distance - plays role in circadian rhythm - reflex (pupils contract/expand from light)
29
What is the pathway of the geniculostriate system?
All P-cell axons & some M-cell axons to LATERAL GENICULATE NUCLEUS (LGN) in THALAMUS THEN processed to area V1 of PRIMARY VISUAL CORTEX (striate cortex) THEN pathway divide and heads into… - Parietal lobe (dorsal stream) - Temporal lobe (ventral stream)
30
What is the pathway of the tectopulvinar system?
Remaining M-cell axons head to the SUPERIOR COLLICULUS In the MIDBRAIN TECTUM THEN info projects to PULVINAR REGION of the THALAMUS ***PULVINAR BYPASSES occipital visual areas - Medial sends to parietal lobe (dorsal) - Lateral sends to temporal lobe (ventral)
31
What is the pathway of the retinohypothalamic tract?
SYNAPSES in the SUPRACHIASMATIC NUCLEUS in the HYPOTHALAMUS Roles in regulating CIRCADIAN RHYTHMS and PUPILLARY REFLEX
32
What is the lateral geniculate nucleus input?
Gets signals predictably: - Input from the RIGHT half of each retina is sent to the RIGHT LGN - Input from the LEFT half of each retina is sent to the LEFT LGN 6 layers in each lateral geniculate nucleus… (different cells and different retinas)
33
What does the occipital cortex input include? (2 types of cortex)
Composed at least 6 visual regions 1. Primary visual cortex (v1, striate cortex) - receives input from lateral geniculate nucleus 2. Secondary visual cortex (v2-v5, extrastriate cortex) - visual cortical areas outside striate cortex
34
What happens to info segregated in LGN?
It MAINTAINS that segregation when sent to ADJACENT REGIONS in CORTICAL LAYER IV
35
What happens in V1 during occipital cortex processing?
Incoming info SEGGREGATED into catergories of COLOUR, FORM & MOTION Blobs = cytochrome oxidase (colour) Interblobs = spaces b/w lobes (form & motion) ***THESE CATERGORIES ARE KEPT SEPERATE AS THEY MOVE FROM V1 —> V2
36
What happens in V2 during occipital lobe processing?
V2 stains DIFFERENTLY than V1 Thick stripes = receive info from neurons (movement) Thin stripes = receive info from neurons (colour) Pale zones = receive info from neurons (form)
37
Where does info from blobs & interblobs in V1 flow to?
Thick, thin and pale zones of V2
38
Where does info from thin zones flow to?
Regions V3 & V4 to FORM the VENTRAL STREAM
39
Where does info from thick & pale zones flow to?
Regions V3A & V5 to FORM the DORSAL STREAM
40
What is the fusiform face area? (FFA)
Located in the FUSIFORM GYRUS on the underside of the brain directly below the INFEROTEMPORAL (IT) CORTEX Identified by Kanwisher et al. Using fMRI Damage can = prosopagnosia ***NOT THE ONLY AREA INVOLVED IN PERCEIVING FACES
41
What is the parahippocampal place area? (PPA)
Located in TEMPORAL LOBE Responds to PLACES (geometry/geometric layout) not objects/faces = SPACIAL LAYOUT HYPOTHESIS * scenes larger responses than buildings * building larger responses than other objects
42
What is the extrastriate body area? (EBA)
Specialized area in the TEMPORAL CORTEX Activated by PICTURES/PARTS of BODIES not faces or objects Catergories (animate VS inanimate objects) = activate specific areas
43
How does the retina work as a coding location?
Light in one place will activate ONE GANGLION CELL and light in another place will activate a DIFFERENT GANGLION CELL
44
How does the lateral geniculate nucleus work as a coding location?
Neurons also have VISUAL FIELDS Each cell represents a PARTICULAR PLACE
45
What is the receptive-field hierarchy?
The RECEPTIVE fields of many RETINAL GANGLION cells ———-> Combine to form the RECEPTIVE field of a SINGLE LGN cell ——> The RECEPTIVE fields of many LGN cells combine to from the RECEPTIVE field of a SINGLE V1 cell
46
What is the role of the corpus callosum? (In vision)
Most of the FRONTAL LOBES are connected via the corpus callosum ***The OCCIPITAL LOBES have almost NO callosum connections ***EXCEPTION: cells that lay along the midline of the visual field (receptive fields overlap)
47
How do the retinal ganglion cells process? VS How do geniculate nucleus cells process?
Respond ONLY to the PRESENCE or ABSENCE of light (not to shape) Concentric circle arrangement CENTER & SURROUND —————————————————— ALSO CENTER & SURROUND
48
What are the “on-center cells” VS the “off-center cells” In retinal ganglion cells?
On-center cells: - EXCITED when light falls on CENTER OF RECEPTIVE FIELD - INHIBITED when light falls on PERIPHERY (surround) ^^^ ***light across whole field = produces weak excitation Off-center cells: - EXCITED when light falls on PERIPHERY (surround) OF RECEPTIVE FIELD - INHIBITED when light falls on CENTER ^^^ ***light across whole field = produces weak inhibition
49
What happens when receptive fields overlap?
Neighbouring retinal ganglion cells RECEIVE their inputs from an overlapping set of PHOTORECEPTORS
50
What is edge enhancement?
INCREASE in perceived CONTRAST at borders b/w VISUAL REGIONS Make edges look MORE distinct so that we can SEE them more easily
51
What is luminance contrast?
Amount of LIGHT REFLECTED by an object relative to its SURROUNDINGS
52
What are simple cortical cells? (In V1)
Excitatory & inhibitory areas arranged SIDE BY SIDE Responds best to BARS of a PARTICULAR ORIENTATION
53
What are complex cortical cells? (In V1)
Responds best to MOVEMENT of a correctly ORIENTED BAR across the receptive field Many cells respond best to particular DIRECTION OF MOVEMENT
54
What are end-stopped cortical cells (aka hypercomplex)? (In V1)
Responds to CORNERS, ANGLES OR BARS of a particular LENGTH moving in a particular direction
55
How is the cortex organized in orientation columns?
Neurons w/in columns fire MAXIMALLY to the SAME ORIENTATION of stimuli Adjacent columns change preference in orderly fashion One millimeter across cortex represents ENTIRE range of orientation Ex) good because in our environment has typical straight vertical and horizontal lines
56
What is a hypercolumn?
Location column with ALL of its ORIENTATION COLUMNS
57
What are ocular dominance columns?
Visual cortex shows this NEURONS in cortex respond PREFERENTIALLY to ONE EYE
58
How does the temporal cortex process shape? What is stimulus equivalence?
Cells are MAXIMALLY EXCITED by COMPLEX VISUAL STIMUI (ex. Faces, hands etc…) May be SELECTIVE to particular faces seen HEAD-ON, posture of head or spec facial expressions Stimulus equivalence: Recognizing an object is the SAME across DIFF viewing orientations
59
What is additive colour mixing?
Superimposes LIGHTS putting more light in the mixture than exists in any one light by itself
60
What is subtractive colour mixing?
REMOVES some wavelengths of light, leaving LESS light than was originally there
61
What is trichromatic theory? Explains “______ _______”
Human eye has 3 TYPES of receptors w/ differing SENSITIVITIES to DIFFERENT wavelengths Specialized recpetors that are sensitive to RED, GREEN & BLUE ALL colours are created by an additive mixing process —————————————————————————— Colour blindness Most ppl who have this are dichromats (red, green or blue insensitive dichromatism)
62
What is opponent-process theory? Explains “__________”
Human eye has 3 TYPES of receptors w/ differing SENSITIVITIES to different light WAVELENGTHS Each CONE is responsive to 2 WAVELENGTHS Occurs in RETINAL GANGLION CELLS EX) red&green, blue&yellow, black&white ————————————————————————- After images Visual image that persists AFTER a stimulus is REMOVED
63
What is dual-process theory?
COMBINES trichromatic & opponent-process theory 3 TYPES of cones, each sensitive to different WAVELENGTHS Cells in retina & visual cortex that respond in OPPOSITE ways to red vs green and green vs blue and blue vs yellow
64
Neurons in cortical region V4 (dorsal stream) do not respond to particular wavelengths, but are responsive to what?
Various PERCEIVED COLOURS The receptive field center is EXCITED by a SPEC COLOUR and the surround is INHIBITED May be important for COLOUR CONSISTENCY
65
The posterior parietal cortex (in the dorsal stream) is involved in processing visual information for?
For ACTION (how/where stream) Some cells in this area process the visual APPERANCE of an object to BE GRASPED Cells will fire even when a monkey watches another monkey pick up an object
66
The “what pathway” is what?
The VENTRAL PATHWAY
67
The “where pathway” is what?
The DORSAL PATHWAY
68
BOTH the ventral (“what” pathway) and the dorsal (“where” pathway) have what in common?
Originate in RETINA & continue through the 2 types of GANGLION CELLS in the LGN Have some INTERCONNECTIONS Receive feedback from HIGHER BRAIN AREAS
69
What happens when there is injury to the “what” (ventral) pathway?
Agnosia: - not knowing Visual-form agonosia: - inability to recognize OBJECTS Colour agnosia (achromatopsia): - inability to recognize COLOURS Face agnosia (prosopagnosia): - inability to recognize FACES
70
What happens when there is injury to the “how” (dorsal) pathway?
Deficits in REACHING or GRASPING objects
71
How do we know? (Lesioning or ablation experiments)
1. Animal trained to indicate PERCEPTUAL CAPACITIES 2. SPECIFIC part of the brain is REMOVED/DESTROYED 3. Animal is retrained to determine which PERCEPTUAL ABILITIES REMAIN = results reveal which portions of the BRAIN are responsible for specific behaviours
72
What happened in the Ungerleider and Mishkin experiment?
1. Object discrimination problem: - monkey shown object - presented with 2 choice task - reward is given for detecting the TARGET object 2. Landmark discrimination training: - monkey is trained to pick the food while next to a cylinder
73
Removal of the temporal lobe tissue in the monkeys showed a problem with what task? Removal of the parietal lobe tissue in the monkeys showed a problem with what task?
(-) Temporal lobe = OBJECT DISCRIMINATION TASK (“how” pathway- ventral) (-) Parietal lobe = LANDMARK DISCRIMINATION TASK (“where” pathway- dorsal)
74
What is selective rearing?
Animals reared in enviro that contain ONLY certain types of STIMULI NEURONS that respond to these stimuli will become more PREDOMINATE due to NEURAL PLASTICITY Ex) cats raised just in horizontal vs just vertical lined enviro
75
“_________” fields locate sensory events. Receptor “________” determine acuity to sensory stimulation
Receptive; density
76
Retinal ganglion cells divide into what 2 catergories?
M-cells (magnocellular): - LARGER M-cells primarily receive their input from RODS - sensitive to LIGHT - found throughout the RETINA P-cells (parvocellular cells): - SMALLER P-cells primary receive their input from CONES - sensitive to COLOUR - found largely in FOVEA *Magno* = Latin means “large” *Parvo* = Latin means “small”
77
Neurons that project into the brain from the retina and form the optic nerve are called “_______ ________ _______”
Retinal ganglion cells (RCGs)
78
Visual acuity is best in the “_______” part of the visual field at the back of the brain Peripheral visual is more “___________” in the brain
Center; anteriorly
79
The visual field is composed of thousands of small “_________ _______” of the retinal ganglion cells
Receptive fields
80
Light stimulates “____________” cells in the retina, which in turn stimulate “_______ ______” cells, the axons of which form the optic nerve. The optic nerve connects to cells in the “_______ _______ ________,” where this visual information is processed to represent location
Photoreceptors; retinal ganglion; lateral geniculate nucleus
81
Inputs to different parts of cortical region V1 from different parts of the retina essentially form a(n) “_____________ _____” of the visual world w/in the brain
Topographic map
82
The two sides of the visual world are bound together as one perception by the “________ _________”
Corpus callosum
83
Each rentinal ganglion cell responds only to the “_________/_________” of light in its receptive field, not to “________”
Presence/absence; shape
84
Neurons in the primary visual cortex respond to properties of shapes, especially to “_____ __ _____” oriented in a certain direction
Bars of light
85
Recognition of complex visual stimuli such as faces is completed in the “_________” lobe
Temporal
86
Retinal ganglion cells mediate colour vision by “__________” processes How does this happen?
Opponent —————————————————————— RCGs are EXCITED by one wavelength of light and INHIBITED by another Producing two pairs of what it seems to be COLOUR OPPOSITES RedVSgreen, blueVSyellow
87
Homonymous hemianopia VS Quandrantanopia?
Homonymous hemianopia: - blindness of one ENTIRE side of the visual field Quandrantanopia: - destruction of only a PART of the visual field
88
What are blind spots also called?
Scotomas Can be a warning symptom for people with migraines
89
Destruction of the retina or optic nerve causes what?
Monocular blindness
***PSYCH 275- Brain & Behaviour
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