L7 - 8 Vision

Question 1

How many areas in the cortex associated with vision? How are these areas differentiated?

Answer 1

30 - diff by rep of visual space and functional properties of neurons

Question 2

What is low level visual processing? Intermediate? High?

Answer 2

Low (retina)

• Colour
• Orientation
• Movement
• Edges
• Contrast

Intermediate (PVC)

• Analysis of layout of scenes
• Distinguishing foreground from background
• Parsing of objects into surface and global contours

High (Beyond PVC)

• Object recognition
• Matching with memories

Question 3

Dorsal pathway - What cortical area is involved?

Answer 3

AREA MT - detecting where an object is, visual processing is through V1, V2, MT

Question 4

Ventral pathway - What cortical area is involved?

Answer 4

AREA IT - object recognition, visual processing through V1, 2, 4

Question 5

Describe the features of a SBAC

Answer 5

• Only dendrites
• Only distal part of cell can send outputs out
• Synapses with DS GC
• GABA is only released when stimulus (light) moves from soma to dendrite (encodes DS)

Input: Glu, GABA, gly
Output: GABA, Ach
*DS has to do with GABA release, nothing to do with Ach (function unknown currently)

Question 6

What does cortical magnification in the brain mean in reference to vision?

Answer 6

The brain uses more physical space for signals from the fovea than the periphery

Question 7

M cells synapse onto which layer of LGN? P cells?

Answer 7

M - 4B, 4C alpha, 6

P - 4A, 4CBeta, 6

Question 8

What is special about neurons in layer 4B?

Answer 8

DS as it gets info from the retina (bigger discharge when left to right)

Question 9

In V1 we have cytochrome oxidase blobs (colour info) - interblobs code for?

In V2 we have thin stripes (____) and thick stripes (____)

Answer 9

Interblobs = orientation sel
Thin = colour
Thick = motion

Question 10

AREA MT not only detects motion but also?

Answer 10

Coherence

Question 11

What do lesions in MST lead to? Why?

Answer 11

Deficits in pursuit eye movements because MST sends info to brainstem for eye movments

Question 12

What do right occipito-parietal lesions lead to?

Answer 12

Deficits in pursuit eye movements

Question 13

V2 makes up _% of all neocortex

Answer 13

10%

Question 14

Object invariance

Answer 14

Doesn’t matter whether horse is facing you sideways or front on - you can still recognise that it is a horse

e.g. A single hippocampal cell responds to multiple presentations of Jennifer Aniston

Question 15

Apperceptive (no perception) agnosia - what is it? where is the lesion?

Answer 15

• Cannot match or copy an object
• Can name object
• Cannot integrate and bind visual info into sensory representations of entire objects

LOCATION: Posterior IT lobe

Question 16

Associative agnosia - what is it? where is the lesion?

Answer 16

• Can match or copy objects
• Cannot name object
• Can integrate and bind visual info into sensory representations of entire objects
• Cannot identify object/cannot associate with meaning

LOCATION: Anterior IT lobe
*Anteriorly (higher level object recognition) has already received input from PVC V2 - higher level of object recognition (hence when lesion is here, object recognition is impaired)

Question 17

What is the function of cytochrome oxidase staining?

Answer 17

Shows metabolic energy and neural activity

Question 18

Complex cells have End zone inhibition/ End-inhibited receptive fields - what does this mean?

Answer 18

Neurons respond to lines of a particular length and curvature

Question 19

V4 neurons have small/large receptive fields that fire to ____ ____ but not simple stimuli (orientation, colour)

There are areas that don’t overlap where one encodes colour and another encodes orientation

Answer 19

Large, coloured patterns

Question 20

The FFA (Fusiform face area) is located on the dorsal/ventral surface of the __ lobe on the medial/lateral side of the fusiform gyrus

For face recognition, 5 regions are linked by?

Answer 20

Ventral, IT, lateral

Horizontal connections

Question 21

How many % of neurons in Fusiform face area patches respond to faces?

Answer 21

97

Question 22

What do neurons in “face-patches” encode?

Answer 22

Neurons encode round objects where shape and aspect of face leads to firing of neurons - there is something about the roundness of the face that stimulates them

Question 23

What happens when you stimulate the FFA?

Answer 23

Makes the subject think you look like someone else

Question 24

Columnar organization of the anterior part of the IT lobe

Answer 24

PVC is organised in columns of neurons that represent the same stimulus feature (e.g. orientation or direction of motion)

Different aspects of faces are encoded in columns

Question 25

Describe the connections of the fusiform face area patches

Answer 25

Stimulation of one patch causes activation in another - there are long horizontal connections between patches

Question 26

Outputs from IT lobe

Answer 26

• Perirhinal and parahippcoampal cortices

- PFC

Question 27

Face recognition is similar/different in MZ twins and similar/different in DZ twins

Answer 27

Face recognition is similar in MZ twins (0.7) and different in DZ twins (0.3)

Question 28

T/F: Neurons in the IT temporal lobe cannot be modified by experience

Answer 28

F - Can be modified by exp

Question 29

Neurons in PFC and IT cortex continuously fire even after the visual image has been removed. What is this continual firing is thought to be important for maintaining?

Answer 29

Short term memories

Question 30

Area IT sends input into which area?

Answer 30

Area IT sends input into amygdala = feelings when seeing visual images

Question 31

C and I organisation of LGN layer

Answer 31

6P- C
5P - I
4P - C
3P- I

2M - I
1M - C