Visual system 3

Question 1

What is the role of area V2 in visual processing?

Answer 1

Area V2 continues the processing of shape that begins in V1 and responds to more complex object properties such as figure/ground segregation, orientation of illusory contours, and retinal disparity.

Question 2

What do cells in area V2 respond to?

Answer 2

Cells in V2 respond to simple properties of objects such as orientation and spatial frequency, like V1 cells. V2 also extends into crotext

Question 3

which complex properties do V2 cells also respond to?

Answer 3

figure/ground segregation- analysis of visual scene on basis of what is object in visual scene and what is the background

orientation of illusory contours -

retinal disparity- humans have 2 eyes and because spaced horizontally- image that right eye receives will be slightly different to left eye

Question 4

How is V2 organized?

Answer 4

V2 is organised in stripes as opposed to columns

Question 5

what are the 3 types of stripes in V2

Answer 5

thin stripes, thick stripes and inter-stripes (also known as pale stripes)

Question 6

where does V2 receive input from?

Answer 6

V2 receives input from both magnocellular and parvocellular cells

Question 7

How does area V2 receive input from magnocellular neurons?

Answer 7

particularly in its thick stripes.

Question 8

where does area V2 receive input from Parvocellular (PI) neurons?

Answer 8

interstripes

Question 9

where does area V2 recieve input from Parvocellular (PB) neurons?

Answer 9

thin stripes

Question 10

What is the primary role of area V3?

Answer 10

Area V3 of visual cortex is involved in processing aspects of motion, specifically, dynamic form and three-dimensional structure from motion

Question 11

What is dynamic form? (V3)

Answer 11

neurons respond to shape information that is defined by motion differences rather than by luminance or contrast differences alone

Dynamic form helps detect what shape is present based on motion

Question 12

what do V3 neurons allow us to do?

Answer 12

V3 neurons allow us to see shapes not just by their edges or colours but also by how different parts move (motion)

Question 13

what is 3D SFM

Answer 13

3D SfM is the ability of the visual system to infer the three-dimensional shape of an object based on its motion, even in the absence of depth cues (lines/shading)

3D structure from motion (3D SfM) helps detect an object’s three-dimensional shape based on movement

Question 14

Is Area V3 part of dorsal or ventral stream?

Answer 14

both

V3 is often considered part of the dorsal visual stream (associated with motion processing) but it also has connections to the ventral stream (linked to form and object recognition)

Question 15

what is Area V4 known for

Answer 15

Area V4 is crucial for visual object recognition, with cells that respond to color and simple stimuli, as well as more complex shapes.

The precise role of V4 in visual processing is not fully understood

Question 16

which area is the first area of visual cortex that is affected by changes in attention?

Answer 16

Area V4

it is not clear how V4 integrates feature analysis and attention processes

Question 18

what do neurons in V4 respond to?

Answer 18

Some cells in V4 respond to relatively simple stimuli like sinusoidal frequency gratings

Other neurons in V4 respond to more complex concentric and radial stimuli (e.g. colour wheels, shapes spinning)

Question 19

what impairments do monkeys with V4 lesions have?

Answer 19

Monkeys with V4 lesions are much more impaired on pattern recognition tasks than they are on colour tasks

Monkeys with V4 lesions can still discriminate hue but are impaired in colour constancy

Question 20

which visual cortex area is concerned with processing colour constancy?

Answer 20

V4 is concerned with processing colour constancy

Question 21

What is color constancy?

Answer 21

Color constancy allows objects to maintain their perceived color despite changes in lighting.

Question 22

what is area V5 involved in?

Answer 22

involved in processing motion

Question 23

what is area V5 also known as?

Answer 23

also known as middle temporal or MT cortex,

Question 24

what do neurons ins area V5 respond to?

Answer 24

to an object’s position, direction of motion, and speed of motion, as well as providing depth information by responding to binocular disparity

Question 25

are V5 neurons the same as V1 neurons?

Answer 25

V5 neurons do not differ from some neurons in V1. V5 neurons have larger receptive fields than V1 neurons; some estimates suggest that they may be ten times larger than V1 receptive fields

Question 26

How is area V5 arranged?

Answer 26

- in columns - Each V5 neuron responds preferentially to a particular speed and direction of motion

Question 27

how are neurons in area V5 grouped?

Answer 27

into direction columns, with direction preference changing systematically either clockwise or anti-clockwise as you move from one column to the next adjacent column

Question 28

what takes place in the inferotemporal cortex?

Answer 28

Complex object recognition is thought to take place in the inferotemporal (IT) cortical area

Question 29

what neurons carry out regnotion of whole objects?

Answer 29

Recognition of whole objects appears to be carried out by specialised neurons in inferotemporal cortex

Question 30

do inferotemporal cells respond to simple or complex stimuli?

Answer 30

Cells in inferotemporal, or IT, cortex respond to more complex shapes that may include combinations of elements as well as motion or texture Most IT cells do not require a natural object such as a face but require moderately complex stimuli

Question 31

How do Inferotemporal neurons have such complex receptive fields?

Answer 31

The complex receptive fields of these IT neurons are probably a result of experience and learning

Question 32

How is the inferotemporal cortex organised?

Answer 32

IT cortex is organised in columns Within one column, cells are grouped according to category and similarity All cells in the same column respond to similar but slightly different stimuli

Question 33

how do cells in inferotemporal cortex respond to complex objects?

Answer 33

Cells in IT will respond to the features of complex objects, and these cells are grouped into columns of cells responding to similar stimulus features

Question 34

what is the parietal cortex important for?

Answer 34

The parietal cortex is important for depth perception and motion perception

Question 35

where are spatiotemporal inputs related to depth and motion integrated?

Answer 35

Spatiotemporal inputs related to depth and motion are integrated and interpreted in parietal cortex

Question 36

what is the two streams hypothesis?

Answer 36

The two-streams hypothesis proposes that the human visual system processes information through two distinct pathways: a dorsal stream for spatial processing and action guidance, and a ventral stream for object recognition and identification. The two-streams hypothesis proposes two main pathways in the brain: the ventral "what" pathway for object identification and the dorsal "where" pathway for motion and spatial processing.

Question 37

where does the ventral pathway start and end?

Answer 37

starts in occipital cortex and ends in temporal cortex

Question 38

which neurons does the ventral pathway receive input from

Answer 38

parvocellular neurons

Question 39

which brain areas contribute to the ventral pathway?

Answer 39

V1 V2 V4 inferotemporal cortex

Question 40

where does the dorsal pathways start and end?

Answer 40

starts in occipital cortex and ends in parietal cortex

Question 41

which neurons does the dorsal pathway receive input from?

Answer 41

magnocellular neurons

Question 42

which brain areas contribute to the dorsal pathway

Answer 42

V1 V2 V3 V5 parietal cortex

Question 43

What happens if area V5 is damaged?

Answer 43

Akinetopsia is a severe impairment in the perception of motion resulting from bilateral damage to V5 (dorsal) Shapes, objects and faces can be identified without difficulty; however, the perception of motion is severely impaired Motion is perceived as abrupt and jerky with sudden changes in the position of an object rather than the smooth perception of an object in motion

Question 44

does damage to V5 abolish all motion perception?

Answer 44

no, Damage to V5 does not abolish all motion perception because other cortical areas such as area V3 are also involved in the processing of motion

Question 45

what can Bilateral damage to the temporal lobes (ventral pathway) result in?

Answer 45

a deficit in object recognition known as visual agnosia Vision, language, memory and intelligence remain intact There are no problems with `seeing’ or understanding or communicating Problem is with the integration and interpretation of visual input in the ventral pathway (seeing without recognising)

Question 46

How does DF’s case study support the separation of the ventral and dorsal streams?

Answer 46

DF showed impairment in perceptual tasks but normal motor (visuospatial) tasks, suggesting separate ventral and dorsal streams. However, later studies found overlap in these pathways.

Question 47

What is the "vision-for-action" vs "vision-for-perception" approach?

Answer 47

This approach suggests that the dorsal pathway is for guiding actions (vision-for-action), while the ventral pathway is for object identification and visual perception (vision-for-perception).