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Biological Foundations of Psychology > (8.2) Visual Systems > Flashcards

(8.2) Visual Systems Flashcards

1
Q

What is the retina?

A

The retina is the sensory organ of vision

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2
Q

What are the three main layers of a retina?

A

photoreceptor, intermediate layer and ganglion cell layer

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3
Q

What is the photoreceptor cell made up of?

A

Photoreceptor layers - Rods and cones (closest to the surface

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4
Q

What is the intermediate layer made up of?

A

Intermediate layer - Bipolar, horizontal, and amacrine cells

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5
Q

What is the ganglion cell made up of?

A

Ganglion cell layer - Retinal ganglion cells: midget & parasol

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6
Q

Rods and cones respond to…

A

light intensity

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7
Q

In darkness, rods & cones constantly release…

A

neurotransmitter (glutamate)

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8
Q

Light is absorbed by a…

A

pigment in rods and cones

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9
Q

change in shape of photopigment triggers a

A

G-protein cascade that reduces glutamate release

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10
Q

photoreceptors are inhibited (deactivated) by

A

light

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11
Q

Photo receptors respond to

A

darkness

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12
Q

When photo receptors respond to darkness they…

A

Pump out neurotransmitters creating action potentials

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13
Q

The intermediate layer Transforms light (brightness) information into

A

contrast information

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14
Q

What are the two types of bipolar cells?

A

ON and OFF

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15
Q

ON bipolar cells are inhibited or exhibited by input

A

inhibited

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16
Q

OFF bipolar cells are inhibited or excited by input

A

excited

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17
Q

What is a Parasol?

A

Large dendritic trees, Combine inputs from many bipolar cells

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18
Q

Small dendritic trees, Combine…

A

inputs from few bipolar cells

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19
Q

What is signal transduction?

A

Receptors translate light into neural signals for light intensity

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20
Q

Signals for light intensity are converted into

A

signals for contrast (differences in light intensity) by bipolar and ganglion cells

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21
Q

What are visual receptive fields?

A

the region of sensory space that evokes a response in a neuron

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22
Q

What are the characteristics of visual receptive fields?

A
  • RFs have a position and a size
  • RFs can have both excitatory and inhibitory sub regions
  • Cells respond to light hitting certain areas
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23
Q

ON RFs respond to an increase or decrease in light intensity

A

increase

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24
Q

OFF RFs respond to an increase or decrease in light intensity

A

decrease

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25
What are the characteristics of Retinal Ganglion Cell Receptive Fields?
- Most have 'centre-surround organisation' | - Opposite response to light in centre and surround
26
Centre-Surround RFs are Formed by...
by Lateral Inhibition neighbouring neurons inhibit each other
27
The LGN consists of ____ layers
six
28
How do LGN layers differ?
- The kind of cells they contain - What type of visual input they receive - Which eye they receive input from - Relay station
29
What are the Two Main Visual Pathways in the LGN?
Magnocellular (M) pathway and Parvocellular (P) pathway
30
What are the characteristics of the -Magnocellular (M) pathway?
- Inner two layers (1 & 2) | - Receive input from parasol ganglion cells
31
What are the characteristics of the Parvocellular (P) pathway
- Outer four layers (3,4,5,6) | - Receive input from midget ganglion cells
32
Receptive fields in LGN are similar to those of...
retinal ganglion cells (circular centre-surround)
33
What is the function of the LGN?
- Relay station between eye and brain - Response properties similar to retinal ganglion cells - But receives massive feedback from cortex - 10x as many connections as from the eye! - First site of attentional gating/enhancement - Sleep-related gating of sensory input to cortex (reticular formation) - Feedbacks info from the cortex
34
What is the V1 primary cortex?
- Also known as the striate cortex - First site of visual processing in cortex - Largest area in the brain
35
Most LGN neurons project to...
V1
36
V1 consists of how many layers?
six layers (like all of cortex) with several of the layers divided into sublayers
37
Layer 4 in the v1 consists of...
Layer 4 divided into 4A, 4B, 4C , 4C
38
Axons from LGN terminate...
(synapse with) cortical neurons in layer 4 (IV) of V1
39
Parvocellular (P) pathway projects to what layer in the V1...
-Project to layer 4C
40
The Parvocellular (P) pathway split into two new pathways...
- P-B pathway: colour (blobs) | - P-I pathway: orientation (interblobs)
41
What layer does the Magnocellular (M) pathway project to?
-Project to layer 4C and then onward to 4B
42
What are cells in 4B sensitive to?
- Cells in layer 4B are sensitive to movement | - Some are binocular and disparity/depth sensitive
43
Most cells in V1 are...
binocular (respond to stimulation in either eye)
44
Cells in layer 4 that receive input from LGN are...
monocular (respond only to one eye)
45
What is ocular dominance?
Most cells respond better to stimulation from one eye or the other
46
What is ocular dominance columns?
Cells preferring each eye are clustered into ~1mm thick slabs
47
What is the function of V1
-Topographic (retinotopic) organisation -Contains a 'map' of the visual field -Detailed maps of orientation, colour, spatial scale, motion direction, 3D depth -Projects to most higher visual areas in cortex -For each part of the visual scene, V1 computes: orientation, spatial frequency, motion, colour, depth
48
-V1 cells respond best to limited range of
temporal frequency (flicker rate; how quickly stimuli change over time)
49
-Cells in the M pathway respond better to fast or slower flicker
fast
50
-Cells in the P pathway respond best to fast or slower flicker
slower
51
Neurons in V1 project to higher or lower visual cortical areas
Neurons in V1 project to higher visual cortical areas (extrastriate cortex): V2, V3, V3A, V4, V5...
52
Projections are...
Projections are topographic - each of these areas also contain a map of the visual field
53
What stimuli does V5 respond to?
V5 (MT): motion (M pathway)
54
What stimuli does V4 respond to?
V4: shape and colour (P pathway)
55
What stimuli does V3/3A respond to?
V3/V3A: motion boundaries and textures (M/P pathways)
56
What are the characteristics of the V2?
- Divided into multiple 'stripes': - Thick stripes (M pathway): Sensitive to orientation and movement, Sensitive to disparity (depth) - Thin stripes (P pathway): Sensitive to colour, Not orientation-selective - Inter-stripes (P pathway): Orientation-selective, Not direction-selective
57
The P pathway projects to
V4
58
Damage to V4 causes...
- Damage to human V4 impairs colour perception - But not clear if human V4 is same as in monkey! - Also involved in shape discrimination
59
The M pathway projects to)
V3/V3A and V5 (MT
60
What are the characteristics of the Cells in V3/V3A
- Selective for orientation | - Respond to motion boundaries (dynamic form)
61
What are the charactertistics of the -Cells in V5 (MT)?
- Selective for motion direction and speed | - Process information on motion and stereoscopic depth

Biological Foundations of Psychology (11 decks)

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