Visual System VI

Question 1

Describe what happens bc v1 rfs are small

Answer 1

they may give misleading info on direction of movement = aperture problem

Question 2

What happens as move up in visual processing

Answer 2

Rfs get larger and larger as move higher up In visual processing
=important bc neurons in v1 suffer from aperture problem but
Neurons in Mt do not = larger rfs, integrate rfs so no aperture problem

Question 3

what is aperture problem

Answer 3

Neuron in v1 = Looking through small hole, sees very tiny patch of world
Ex = rectangle with repeating lines moves left to right but v1 sees motion downwards = cannot see what whole object doing
Ex = diamond, v1 neuron only sees edge moving upwards
So v1 neuron = gives inaccurate info about movement of object

Question 4

do neurons in Mt suffer from aperture problem = why or why not

Answer 4

NOOO they don’t suffer from aperture problem
= integrate input from neurons with smaller rfs, so can detect overall direction of movement of an object
Can see = assembled together and detect direction of whole object
Larger rfs = important for understanding global features of objects/motion

Question 5

what does dorsal stream contribute to

Answer 5

Multimodal sensory pathways from parietal cortex to pre motor cortex = that are involved in transforming perception into action

Question 6

describe what happens in dorsal stream = parietal lobe

Answer 6

Parietal lobe = convergence area, higher order cortical somatic sensory area
= where vision, somatic sensory (and auditory) converge together
= info assemble and used to guide motion
Need to integrate somatic sensory and vision like for when grab things
So this integrative info then projects forward to higher order movement region and visual reads = use visual and somatic sensory info to guide movements
Parietal lobe and motor areas interact to use sensory info to guide movement

Question 7

What is ventral stream involved in

Answer 7

Perception of colour vision, form and object recognition (detect and name)
V1–> ventral parts temporal lobe to end of temporal lobe
Ability to see world and assign names/objects = ventral stream and temporal lobe ventral parts

Question 8

what is ffa

Answer 8

Fusiform face area
= in fusiform gyrus, ventral surface of brain
Temporal lobe
Larger on right side = lateralization
Studied a lot - humans and other primates = very important that they can recognize faces

Question 9

what do neurons in ffa respond to

Answer 9

Respond preferentially to faces

Question 10

what do neurons in ffa respond to = describe exp

Answer 10

record aps- face neurons in monkey cortex
For monkey face = fire lots, cartoon monkey face = fire but less vigorous - as remove facial features (—>circle)= none
:. Some ventral stream neurons respond specifically to faces
=neuron detects face, in front, on side, far, close, big rf, tuned specifically to faces = larger rf and more specific/specialzied

Question 11

what is prosopagnosia and explain

Answer 11

Loss of ability to recognize familiar faces
- if stoke/neurodegeneration
- higher order damage, more selective, peculiar deficits
-vision ok = can see face and recognize facial features, but if show mother face = wont recognize as mom= cannot inter gate info - for familiar faces

Question 12

what is brain organized into = clusters of neurons

Answer 12

Clusters of neurons in localized regions respond preferentially to different types of visual objects
Specific areas specialzied for diff things = face areas, hand areas, sensitive to living things, sensitive to inanimate obejcts
If damage areas for colour vision = cannot see or imagine colour, cannot create perception of colour, but can still see fine

Question 13

what happens to rfs as go to progressively higher levels in visual hierarchy

Answer 13

Rfs get progressively larger at progressively higher levels in visual hierarchy

Question 14

describe reciprocal connectivity in visual processing = gen

Answer 14

There are extensive short and long range reciprocal connectivity low and high levels in visual processing

Question 15

describe reciprocal connectivity in visual processing = specifically what happening

Answer 15

<—> = at every level 2 way connections = goes both ways, reciprocal connections
True for almost all connections in visual pathway
Lots of feedback, higher —> Lower level
= have to build up visual perception from bottom up
But also have top down mechanisms which are important…

Question 16

describe top down mechanism

Answer 16

Feedback connections may be involved in visual attention and in top down anticipatory mechanisms that enable us to differentiate an object from the background
Ex= blotches, see face, now blotches = face = top down control, = can organize what’s coming up, enabling anticipation fo what’s coming up = organize what is being fed forward
Can switch back and forth = have control and decide which to see = top down control = decide how sensory info organized

Question 17

Define predictive processing

Answer 17

Theory of sensory perception
Model of sensory perception

Question 18

what is happening in predict processing = specifically

Answer 18

Higher levels in sensory hierarchy feed perceptual expectations back to lower levels
This Feedback is compared with sensory input
Differences between feedback expectation and feed forward create a prediction error signal that is fed forward to update the predictive model at the next level in hierarchy

Question 19

what is happening in predict processing = generally

Answer 19

Imagine if vision bottom up only = visual system would have to continuously recreate world over and over again = very inefficient
Instead= constructs visual perception and feeds it back to lower levels so then tells lower levels to only feed up images that change perception
Higher levels maintain stable perception of world
Feedforward from lower levels = what changes, if some movement or object or something

Question 20

what is ex of predictive processing

Answer 20

Image with lines and dots that move around depending where you look
= stable perception of world- fills pattern in for you
Only when move eyes around = see other dots and has to reorganize pattern

Question 21

Describe Medial parts temporal lobe - ventral stream

Answer 21

Medial parts temporal lobe = hippocampus
- learning and memory (ventral stream connected to this too)