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Spring 2025 > PSY368 Section 3 > Flashcards

PSY368 Section 3 Flashcards

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1
Q

Most cones are in the ____ and most rods are in the ____

A

fovea; peripheral retina

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2
Q

How does the difference in ganglion convergence factors between rods and cones affect the function of each?

A

A ganglion cell in the peripheral retina receives input from many rods (high convergence; low visual acuity)
A ganglion cell in the central retina receives inputs from only a few cones (low convergence; high visual acuity)

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3
Q

How does the antagonistic center-surround organization of a cell impact the firing rate?

A

As the light stimulus is presented on the excitatory center, action potentials and firing rates increase. The firing rate returns to baseline once light is presented over both the excitatory center and inhibitory around as they neutralize the response of each other.

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4
Q

Parvo (P) cells

A

recieve most of their input from cones; most common at the fovea
relatively small region of “sight”

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5
Q

Magno (M) cells

A

receive most of their inputs from rods; more common in the periphery
relatively large region of “sight”

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6
Q

Transient response

A

when a stimulus is presented, the cell responds, then it returns to baseline firing (M cells)

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7
Q

Sustained Response

A

a sustained response means the response is continued as long as the stimulus is present

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8
Q

Due to their ___ response, M cells are well-suited to code ___

A

transient; motion

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9
Q

Due to their ___ response, P cells are well-suited to ____ ____

A

transient; form analysis

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10
Q

Retinotopic mapping (definition)

A

spatial info is preserved by many visual structures in the form of topographic maps; in the retina these maps correspond brain space to retinal space

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11
Q

Neighboring points in space are coded in _________

A

neighboring locations in your retina

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12
Q

Spatial information is ____ by the optics of the eye

A

Distorted

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13
Q

Describe the distortion of spatial information by the retina

A

Objects on our retinas are flipped horizontally and vertically relative to their spatial position in the world; this coding is preserved through our brain

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14
Q

Objects appearing in the left visual field are represented in the ________

A

right hemisphere (right V1)

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15
Q

Objects appearing in the right visual field are presented in the ______

A

left hemisphere (left V1)

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16
Q

Geniculostriate Visual Pathway connects

A

the retina (both M & P) to the LGN and the LGN to the primary visual cortex

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17
Q

The geniculostriate visual pathway is mostly responsible for

A

information processing (e.g. pattern analysis)

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18
Q

Structure and organization of the LGN

A

Bilateral structure; one in each brain hemisphere
Retinotopically organized
Consists of 6 spatially-aligned layers

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19
Q

There is ____ in the signal processing occurring in the ganglion cells vs. Tthe LGN cells

A

no difference

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20
Q

The majority of inputs to the LGN are from ____, while the rest are from the _____

A

Cortex (80%); Retina (20%)

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21
Q

The primary visual cortex is the _____ stop in the geniculostriate pathway

A

last

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22
Q

Structure of the V1

A

Bilateral structure
Very large in comparison to LGN
Also consists of layers
Projects to IVc

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23
Q

The IVc is the first place where

A

visual information is actually reaching the brain

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24
Q

Cells in layer IVc of V1 have the same center-surround receptive fields found in the _____ and the _____

A

LGN; retina

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25
Cells with more complex RFs are found in the
surrounding layers of the V1
26
Cells with complex RFs
simple cells complex cells end-stopped cells
27
Simple Cells
Above and below the primary IVc layer Elongated RFs rather than circular Still center-surround antagonistic Respond to stimuli having a particular spatial orientation
28
Simple cells function as
"feature detectors" for oriented edges and bars
29
Complex Cells
tuned for both orientation and direction of motion RFs slightly larger
30
Receptive fields get larger in certain cells in order to
combine properties integrated over a larger area of space
31
Complex cells function as
simple cells tuned for motion (orientation is very important, direction of motion less important)
32
End-Stopped Cells
tuned for orientation, direction of motion, and now size or shape of a stimulus larger RFs than complex cells
33
End-Stopped Cells function as
Length detectors, width detectors, and angle detectors
34
Visual feature analysis
Steady progression of signal processing that allows you to see an edge-detected image. Another part of the brain codes for color, another part for motion, etc. This is how our perception is built up from analyses from different parts of our brain analyzing the same complex stimulus
35
Cortical Magnification in the V1
a relatively big area of V1 is devoted to analyzing info from the relatively small foveal region of the retina (high cortical magnification)
36
Columnar Organization
cells in the V1 are grouped into three types of columns: location, orientation, and ocular dominance columns
37
Cells in columnar organization each
code for the same properties and have the same function
38
Different locations across the surface code for
different locations in space and stimulus properties
39
Location columns
each column is coded for a different region of visual space (overlapping receptive fields
40
Ocular Dominance Column
within each location column, there are two ocular dominance columns cells within a given column respond best to stimuli at a given location as seen through a given eye
41
Orientation Columns
within each location and OD column, there are several orientation columns each column codes an orientation (every ~10 degree of angle is coded by a different column) cells within the same column code the same organization
42
The low-level visual pathway is the
geniculo-striate pathway
43
The High-Level Visual pathways
Dorsal and Ventral Pathways
44
Ventral Pathway
complex pattern analysis leading to object recognition (what)
45
Dorsal Pathway
analysis leading to object localization (where; better described as how)
46
In humans, damage to MT may result in
motion blindness (Akinotopsia)
47
Spatial Hemi-Neglect
damage to the right parietal cortex results in difficulty attending to objects appearing in the left visual field (or vice versa)
48
Inferotemporal Cortex
cells in IT appear sensitive to complex objects consisting of distinct parts
49
IT cells are ____ to an object's spatial location and size
insensitive (location and scale invariant)
50
Some IT cells are highly selective for ___
faces
51
Damage to Inferotemporal cortex
Visual form Agnosia - difficulty recognizing objects Prosopagnosia - specialized form of agnosia resulting in difficulty recognizing faces
52
How did patient DF provide evidence for "What" and "How" pathways
Patient DR suffered damage to her temporal lobe (ventral pathway), leaving her with an inability to recognize objects (visual form agnosia) Damage to the dorsal pathway disrupts our ability to spatially interact with objects, BUT she could put the card into the slot. This provides evidence for two separate processing pathways: "what" and "how"
53
In humans, face-selective cells are found in the _____
fusiform face area in the inferotemporal cortex
54
Color perception (definition)
our capacity to perceive and discriminate light based on its wavelength composition
55
Observation by Isaac Newton about the visual spectrum
He demonstrated that a pinpoint beam of light passed through a prism is refracted and split into a number of rays corresponding to the different wavelengths of light (white light is a combination of all the colors)
56
Why do we perceive a particular color?
Properties of the light How the light is absorbed and reflected The mechanisms of our visual system
57
Physical vs. Psychological Dimensions (Properties of light)
Wavelength - Hue intensity - Brightness Whiteness - Saturation
58
When a short wavelength light passed through a denser medium, it is bent [less/more] compared to a longer wavelength light
more
59
As a light becomes less intense,
we perceive the light as being elss bright
60
A saturated light is a
pure spectral hue (vivid) with no white light mixed in
61
Color Spindle
Visually demonstrates the relationship between hue, saturation, and brightness
62
Color circle
a circular arrangement reflecting the perceptual similarity between different hues (notice that some reds look similar to violets; hence circle rather than line)
63
Additive mixing
Combining two or more monochromatic lights to create a new light having a different hue (the dominant hue often determines how we name the light)
64
Subtractive Mixing
subtracting wavelength from a mixture of light to create a light having a different hue (e.g. cyan and yellow paint mixture gives green since neither absorb green)
65
When adding together wavelengths of light, the resulting product was ____ than the two mixed colors. When subtracting wavelengths, the resulting mixture will be ___ than the original colors.
lighter; darker
66
Trichromacy Theory
Explains that color vision results from the activity of three cone photoreceptors with different spectral sensitivities (long, medium, short wavelength receptors)
67
The ratio of activity among these three cone receptor mechanisms (trichromacy theory) determines our
color percept
68
Color-Matching Task
task where subject matches the hue of a standard color by adjusting the additive color mixture of two or more comparison lights (evidence for trichromacy theory)
69
When the visual system is exposed to light all three cone photoreceptors will fire at different rate because
they are differentially tuned to different wavelengths
70
The ratio of firing of different cone photoreceptors codes for
our perception of color
71
Distributed Coding
representing a pattern as activity distributed over many neurons or neuronal groups
72
Graceful degradation (definition)
losing one neuron group does not mean all that info about a face is lost
73
Just as faces may be coded by a unique ration of activity within three neuron groups, the visual system codes ____
color by the ratio of activity in three cone photoreceptors
74
Opponent process theory (OPT)
3 receptor systems combine to form 3 opponent systems that respond in opposite ways to different wavelengths of light
75
The opposition in OPT is created by
lateral inhibition
76
Evidence for OPT
Color Afterimages Color Blindness
77
Color Afterimages
neural fatigue in one component of an opponent system cause the opposing component temporally dominate perception under equal stimulation (i.e. white) conditions
78
Color Blindness
people have difficulty seeing pairs of colors; suggesting that these colors are paired in separate systems
79
Types of Color Blindness
Rod Monochromatism (complete color blindness) Dichromatism (partial color blindness)
80
Types of Dichromatism
Protanopia (missing L (red); red/green color blind) Deuteranopia (missing (M) (green); red/green color blind) Tritanopia (missing S (blue); blind to blue/yellow)
81
Unilateral Dichromat
person with normal color vision in one eye and dichromatic color vision in the other eye
82
Electrophysical Evidence for OPT
Achromatic vs. Color-Center surround cells
83
Achromatic On-center/off-surround cells
the excitatory center and the inhibitory surround are antagonistic; a white light falling in the center of this cell increases the response and light falling in the surround decreases its response
84
Color Red On-center/green-off surround cells
coding is opponent in the sense that only red or green can be coded, not both; LW light in the center increases response, LW into the surround does NOT decrease the response; MW light falling in the center of the cell does not change the response, MW in the surround will inhibit the cell's response
85
"if the cell is firing above baseline, it is signaling red; If it is firing below baseline, it is signaling green" - This is an example of the
Color-Center Surround Cells
86
Double Opponent Cells
cells in V4 use an antagonist center-surround RF to code color (firing increases when red light falls on the center, decreases when the light extends into surround; firing decreases with green light falling on the center, increases when light extends into the surround)
87
How is spatial information represented in the visual system?
spatial info is preserved in the form of topographic maps (retinotopic)

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