Chapter 3 - Beyond the Striate Cortex - The Extrastriate Cortex

Question 1

What is the orientation selectivity at the cortex attributed to?

Answer 1

Synapse pattern of circular concentric receptive fields of the LGN to simple cells of V1

• multiple simple cells with slightly different orientation selectivity will synapse with a neuron in V4 (this neuron will be selective to contours)
• original mapping can be traced back to the retinal cells

Question 2

What is V2 responsible for?

Answer 2

Complex motion processing

Question 3

What is the aperture effect?

Answer 3

Selective for motion only in the receptor field (cells in V1)
separation of information

Question 4

With which four characteristics can visual areas in the brain be compared?

Answer 4

1. differ according to the types of distributions of neurons within them
2. differ according to the other areas in the brain from which they receive signals or to which they send signals
3. differ according to properties to which their constituent neurons are tuned
   - direction in motion, colour, orientation, form
4. each visual area contains a retinotopic map of the visual field

Question 5

What are the two streams of information flowing out of V1?

Answer 5

1) the dorsal stream

2) the ventral stream

Question 6

Describe the dorsal stream

Answer 6

• the “where” pathway
• passes from V1 to V2, into MT and towards the parietal lobe
• responsible for representing properties that relate to an object’s motion or location (leads to guided action)

Question 7

Describe the ventral stream

Answer 7

• the “what” pathway
• passes from V1 to V2, to V4 and inferotemporal cortex
• responsible for representing properties that relate to an object’s identity (shape, colour)

Question 8

Describe patient “D.F”

Answer 8

• had visual form agnosia (inability to recognize objects by their shape in spite of the ability to see them)

Question 9

What is the simple dichotomy between the dorsal and ventral streams?

Answer 9

• many interactions
• feedforward and feedback processes
• pathways that connect both the ventral and dorsal stream

Question 10

What is blindsight?

Answer 10

Individuals that are cortically blind (damage to striate cortex) can still respond to visual stimuli at a higher than chance level - which means that information is not travelling through the stereotypical pathways of vision
- individuals have no conscious experience of vision, but still respond to visual stimulation

Question 11

What is V4 responsible for?

Answer 11

colour, edges and curvatures

Question 12

What are the LOC and IT responsible for?

Answer 12

objects, faces and places

Question 13

What is the MT responsible for?

Answer 13

Motion

Question 14

What is the fusiform face area?

Answer 14

a subregion of the inferotemporal cortex where cells prefer to respond to faces

Question 15

What do cells in the FFA respond to?

Answer 15

faces and other stimuli that contain similar features to faces
- fine detail discrimination

Question 16

What are some other modules in the IT?

Answer 16

1. the parahippocampal place area (PPA) - selective to scenes
2. extrastriate body area (EBA) - selective to body parts

Question 17

How do we develop modules that are selective to very specific features?

Answer 17

Natural selection