Primary Visual Cortex and Beyond

Question 1

What does contrast sensitivity vary with?

Answer 1

Spatial frequency

Question 2

Which retinogeniculate pathway would be required to resolve the highest spatial frequencies?

Answer 2

Parvocellular pathway

Question 3

Which retinogeniculate pathway would be required to resolve the highest temporal frequencies?

Answer 3

Magnocellular pathway

Question 4

What is the modulat hypothesis of visual function?

Answer 4

• Functional specialisation of the visual cortex
• Parallel nd separate processing of the image attributes in the different cortical areas (colour, form, motion)

Question 5

Outline the pathway of magnocellualr cells

Answer 5

• The projections from V1 LGN go to the thick stripe of V2
• Then there are projections to the dorsal MT (V5) to process motion

Question 6

Outline the pathway fo parvocellular cells

Answer 6

• The projections from V1 LGN go to the thin stripe of V2
• Then there are projections to the ventral V4 to process colour

Question 7

What do the dorsal and ventral streams detect?

Answer 7

Dorsal - spatial
Ventral - object recognition

Question 8

What has been used as evidence to support functional specialisation?

Answer 8

• lesion studies
• neuropsychological assessments following focal brain damage in humans
• electrophysiology
• imaging

Question 9

What are the properties of neurons in the inferotemporal cortex?

Answer 9

• Large RFs extending across the midline usually including the fovea
• Response invariant - retinal size and precise position within the RF doesn’t affect response
• Many cells are ‘face’ cells but other patterns can be effective and may be modifiable with training and attention

Question 10

What is the neuron doctrine?

Answer 10

• Idea that neural responses become increasingly selective at higher stages in neural pathways
• Specific elements of our perceptions are caused by activation of specific populations of neurons, selective for those elements
• Termed as either cardinal or grandmother cells
• Implies population size must decrease as selectivity increases, sparse coding

Question 11

What is the function of motina in the visual stimulus?

Answer 11

• Helps figure out ground segregation
• Draws attention
• Location and navigation

Question 12

How is motion detected?

Answer 12

• Detectors with delay line
• Illusions of visual motion also suggestive of specialised motion processing subsystem

Question 13

What is the modular hypothesis of visual function?

Answer 13

• Functional specialisation of the visual cortex
• Parallel and separate processing of image attributes in different cortical areas (colour, form, motion)

Question 14

How is motion processed?

Answer 14

• receives input from M pathway via V1 & V2
• Retinotopically mapped
• Cells sensitive to direction and speed of motion
• Columnar organisation

Question 15

Global v Elemental Visual Motion

Answer 15

• some V1 cells are sensitive to moving oriented edge
• Consider aperture problem

Question 16

Plaid gratings and motion

Answer 16

• elemental motion components are the direction of each grating
• Superimposed - there is a global motion component
• Many cells in MT area response to global motion - All in V1 respond to elemental