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Perception > Task 4: Columns and pathways > Flashcards

Task 4: Columns and pathways Flashcards

1
Q

Central visual pathway

A

Retina -> Optic chasm -> Lateral geniculate body -> Area V1 primary visual cortex (striate cortex) in occipital cortex

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2
Q

Compared to the actual visual field, the retinal image is

A

inverted and reversed

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3
Q

What happens to the “image” in the optic chiasm?

A

In the optic chiasm:
1- axons from the temporal halves of each retina continue into the optic tract on the same side
2- axons from the nasal halves cross to the optic tracts on the contralateral side

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4
Q

Axons in the optic tract can terminate in

A

mostly = lateral geniculate nucleus

some axons = superior colliculus

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5
Q

The left primary visual cortex gets input from both eyes but

A

only from the right visual field

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6
Q

Lateral geniculate nucleus

A
  • in the thalamus
  • each LGN cell respond to one eye or another, but never to both eyes
  • concentric receptive fields
  • six layered structure
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7
Q

The six layers in the LGN are separated by

A

koniocellular cells

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8
Q

The layers of the LGN are called

A

Magnocellular and Parvocellular layers

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9
Q

Magnocellular layers

A
  • bottom two layers
  • input from M ganglion cells => large cell bodies
  • fast-moving and large objects
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10
Q

Parvocellular layers

A
  • top four layers
  • input from P ganglion cells => small cell bodies
  • stationary targets
  • details : colour, texture, pattern, depth
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11
Q

Topographical mapping of the LGN

A

Contralateral layers: 1, 4 and 6
Ipsilateral layers: 2, 3 and 5

Right visual field = different layers of left LGN

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12
Q

V1 or Striate cortex =

A

Primary visual cortex

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13
Q

Features of V1

A
  • retinotopy

- cortical magnification

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14
Q

Cortical magnification

A

visual acuity declines in orderly fashion with the distance from fovea

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15
Q

Retinotopy

A

orderly mapping = where things are in space (layer 3 in striate cortex = position 3 in visual field)

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16
Q

Properties of receptive fields in the striate cortex

A
  • RF of V1 have an elongated shape
  • selective responsiveness to orientation (better response to horizontal and vertical lines), spatial frequency and ocular dominance
17
Q

Types of cortical V1 Neurons

A

Simple cells
Complex cells
* end-stopped cells

18
Q

Simple cells

A
  • clearly defined excitatory and inhibitory regions
  • sensitive to orientation and contrast
  • phase sensitive = position in the receptive field (response only to centre)
  • edge detector = light on one side of RF and darkness on the other
  • stripe detector = line of light surrounded by darkness
  • ocular preference
19
Q

Complex cells

A
  • no clearly defined excitatory and inhibitory regions
  • no specific on/off centre
  • phase insensitive (position in the RF is irrelevant)
  • sensitive to movement
  • ocular preference
20
Q

End-stopped cells

A
  • subclass of simple and complex cells
  • the cell first increases its firing rate as bar length increases to fill up the receptive field, and then decreases
  • sensitive to corners, angles and lengths
21
Q

Hypercolumn

A
  • analyses all visual features in a small part of visual field
  • two sets of column (orientation and location)
  • covers every possible orientation
  • ocular dominance slabs
22
Q

Streams for vision

A

Ventral Pathway = what

Dorsal Pathway = where/how/action

23
Q

Ventral pathway

A
  • what = object identity and recognition
  • parvocellular system
  • P ganglion cells to inferior temporal lobe
  • high-resolution sensitivity
  • sensitive to form, patter, colour
  • damage = visual agnosia
24
Q

Dorsal pathway

A
  • where/how = action
  • magnocellular system
  • M ganglion cells -> V1 -> parietal lobe
  • determine object location
  • information how to direct action toward stimulus
  • damage = optic ataxia
25
Q

Both Ventral and Dorsal pathways are not

A

entirely separated = have connections between them

26
Q

In neuropsychology, effects of brain damage can be understood by determining

A

double or single dissociation

27
Q

Double dissociation

A

determine whether two functions operate independently from one another
- involves two people with lesions to different brain areas

28
Q

Other higher-level visual areas

A

FFA - fusiform face area = faces
PPA - parahippocampal place area = houses and scenes
EBA - extra striate body area = body shapes
LOC - lateral occipital complex = scrambled images
VWFA - visual world form area = alphabetic strings

29
Q

Visual agnosia

A
  • unable to recognise objects, faces, pictures
  • disabled perceptual experience
  • damage in occipitotemporal region
30
Q

Optic ataxia

A
  • unable to reach objects accurately
  • no difficulty recognising
  • damage to posterior parietal region

Perception (9 decks)

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