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

(8.2) Visual Systems Flashcards

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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
Q

What are the characteristics of Retinal Ganglion Cell Receptive Fields?

A
  • Most have ‘centre-surround organisation’

- Opposite response to light in centre and surround

26
Q

Centre-Surround RFs are Formed by…

A

by Lateral Inhibition neighbouring neurons inhibit each other

27
Q

The LGN consists of ____ layers

A

six

28
Q

How do LGN layers differ?

A
  • The kind of cells they contain
  • What type of visual input they receive
  • Which eye they receive input from
  • Relay station
29
Q

What are the Two Main Visual Pathways in the LGN?

A

Magnocellular (M) pathway and Parvocellular (P) pathway

30
Q

What are the characteristics of the -Magnocellular (M) pathway?

A
  • Inner two layers (1 & 2)

- Receive input from parasol ganglion cells

31
Q

What are the characteristics of the Parvocellular (P) pathway

A
  • Outer four layers (3,4,5,6)

- Receive input from midget ganglion cells

32
Q

Receptive fields in LGN are similar to those of…

A

retinal ganglion cells (circular centre-surround)

33
Q

What is the function of the LGN?

A
  • 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
Q

What is the V1 primary cortex?

A
  • Also known as the striate cortex
  • First site of visual processing in cortex
  • Largest area in the brain
35
Q

Most LGN neurons project to…

A

V1

36
Q

V1 consists of how many layers?

A

six layers (like all of cortex) with several of the layers divided into sublayers

37
Q

Layer 4 in the v1 consists of…

A

Layer 4 divided into 4A, 4B, 4C , 4C

38
Q

Axons from LGN terminate…

A

(synapse with) cortical neurons in layer 4 (IV) of V1

39
Q

Parvocellular (P) pathway projects to what layer in the V1…

A

-Project to layer 4C

40
Q

The Parvocellular (P) pathway split into two new pathways…

A
  • P-B pathway: colour (blobs)

- P-I pathway: orientation (interblobs)

41
Q

What layer does the Magnocellular (M) pathway project to?

A

-Project to layer 4C and then onward to 4B

42
Q

What are cells in 4B sensitive to?

A
  • Cells in layer 4B are sensitive to movement

- Some are binocular and disparity/depth sensitive

43
Q

Most cells in V1 are…

A

binocular (respond to stimulation in either eye)

44
Q

Cells in layer 4 that receive input from LGN are…

A

monocular (respond only to one eye)

45
Q

What is ocular dominance?

A

Most cells respond better to stimulation from one eye or the other

46
Q

What is ocular dominance columns?

A

Cells preferring each eye are clustered into ~1mm thick slabs

47
Q

What is the function of V1

A

-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
Q

-V1 cells respond best to limited range of

A

temporal frequency (flicker rate; how quickly stimuli change over time)

49
Q

-Cells in the M pathway respond better to fast or slower flicker

A

fast

50
Q

-Cells in the P pathway respond best to fast or slower flicker

A

slower

51
Q

Neurons in V1 project to higher or lower visual cortical areas

A

Neurons in V1 project to higher visual cortical areas (extrastriate cortex): V2, V3, V3A, V4, V5…

52
Q

Projections are…

A

Projections are topographic - each of these areas also contain a map of the visual field

53
Q

What stimuli does V5 respond to?

A

V5 (MT): motion (M pathway)

54
Q

What stimuli does V4 respond to?

A

V4: shape and colour (P pathway)

55
Q

What stimuli does V3/3A respond to?

A

V3/V3A: motion boundaries and textures (M/P pathways)

56
Q

What are the characteristics of the V2?

A
  • 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
Q

The P pathway projects to

A

V4

58
Q

Damage to V4 causes…

A
  • Damage to human V4 impairs colour perception
  • But not clear if human V4 is same as in monkey!
  • Also involved in shape discrimination
59
Q

The M pathway projects to)

A

V3/V3A and V5 (MT

60
Q

What are the characteristics of the Cells in V3/V3A

A
  • Selective for orientation

- Respond to motion boundaries (dynamic form)

61
Q

What are the charactertistics of the -Cells in V5 (MT)?

A
  • Selective for motion direction and speed

- Process information on motion and stereoscopic depth

Biological Foundations of Psychology (11 decks)

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