Visual System V

Question 1

what are v1 neurons organized into

Answer 1

Orientation selective columns
(Vertical, also ahve many diff types columns in v1)

Question 2

describe the organization of columns in v1

Answer 2

Columns arranged in complex pattern of swirls = spiral for specific location in visual space
Cycle around swirl contains neurons responding to full range of orientations for a specific location in space
= whole thing = functional unit, all possible ordinations of bars of light for one region
(Diff types of cells, simple, complex, selective to moeevmnt, but ALL selective to bar at specific orientation)

Question 3

how were orientation selective columns mapped

Answer 3

Electrodes = see all neurons respond to bar at specific orientation - all the way down
Move over = all neurons in next column respond to bar at diff orientation = mapped orientation columns
Now use optical imaging

Question 4

Describe rf complex cell

Answer 4

Do not have inhibitory surround region in rf
= complex cell responds to bar at specific orientation at any location in rf
Good for detecting edges

Question 5

how did rf complex cell happen

Answer 5

Built up from input of simple cells, convergence of simple cells

Question 6

what are some cells in v1 selective to

Answer 6

Some respond best to bars of light moving in one direction

Question 7

describe end stopped cells in v1

Answer 7

Neurons sensitive to bar length
Bar of light at specific orientation - has to end within cells rf
= good for detecting ends of line segments - important for detecting motion

Question 8

describe blobs = where and neurons

Answer 8

Interspersed with orientation columns
Neuron in blobs tend to be more responsive to colour, less sensitive to stimulus orientation
Cylinder of cells - inserted in layer 2 and 3, another type of columns found, clusters of cells = detected using certain kinds of metabolic stains
Input from k m and p pathways

Question 9

describe ocular dominance columns= specifically

Answer 9

Super imposed on orientation columns and blobs are columns corresponding to alternating input from ipsilateral and contralateral eyes = called ocular dominance columns
Info = separate up to layer 4, get input form diff eyes, each column prefers one eye or other

Question 10

describe ocular dominance columns = gen

Answer 10

Spiral =columns that respond to bars of light of a particular orientation, then have spiral for all orientations - ipsilateral eye
Functional units = blobs and all orientations= tiles v1
Many columns super imposed onto each other

Question 11

describe ocular dominance columns = center

Answer 11

especially ahve specific preference for one eye or other
Not cylinders

Question 12

how does visual info flow from v1

Answer 12

Through separate dorsal - where and ventral - what streams

Question 13

describe dorsal stream

Answer 13

Encodes location and movement
Parietal lobe
Heads
Location, movement, guide action

Question 14

describe ventral stream

Answer 14

Encodes form and colour
Travels along ventral part
Temporal lobe

Question 15

describe dorsal and ventral streams in macaque

Answer 15

Many regions identified in monkeys
Stream interact =not completely separate

Question 16

what is area Mt macaque

Answer 16

In dorsal stream
Involved in detection of motion

Question 17

describe what happens when lesion Mt neurons macaque

Answer 17

Produce deficits in detecting global motion

Question 18

describe what happens when lesion Mt neurons macaque = describe test - dot coherence

Answer 18

Random dot coherence = can vary coherence = varies difficulty
Usually 5-10% correlation = can detec motion
But if lesion = cannot detect motion
For humans = lesion here = akinetopsia = cannot detect motion = see stop motion
:. Area Mt very important for detecting visual motion