Visual System Function: Central Vision Processing

Question 0

LGN Layers 3-6

Answer 0

Parvocellular

*Contains axons of P-type RGCs, have small fields, and respond w/ sustained firing

Question 1

LGN Layers 1,2

Answer 1

Magnocellular

*Contain axon from M-type RGCs, have large receptor fields, and respond to stimulation w/ transient spiking

Question 2

Layer IVCa

Answer 2

Receives axons from Layers 1,2 of LGN; have oval shaped receptor fields that are orientation selective

=>projects to Layer IVB

Question 3

Layer IVCb

Answer 3

Receives axons from LGN Layers 3-6
Cells are binocular; are orientation AND direction sensitive

*Allows for the analysis of motion

=>projects to Layer III

Question 4

Layer III (Primary Visual Cortex)

Answer 4

Receives axons from intralaminar neurons in LGN

Question 5

P-IB (Parvocellular interblob channel)

Answer 5

Allows for detection of shape via orientation of receptive fields

• Are found in b/w the blobs of Layer III
• Are binocular & insensitive to wavelength

Question 6

Blob Channel

Answer 6

Allows for analysis of color via wavelength sensitive, monocular cells

Question 7

Dorsal Stream of Extrastriate Visual Cortex

Answer 7

Layer IVB M-channel neurons project to…

1. Area MT- shows directional tuning and responds to movement
2. Area MST- Responds to complex motions (Rotation, linear motion)

Question 8

Ventral Stream of Extrastriate Visual Cortex

Answer 8

Blob and interblob neurons of Layer IVC project thru…

1. Area V4- Large receptive fields that contribute to color analysis and perception
2. IT Areas- Respond to colors and highly specific shapes

Question 9

Achromatopsia

Answer 9

Lesion in V4 that results in partial/complete loss of color vision

Question 10

Prospagnosia

Answer 10

Lesion in IT areas where pts. are unable to identify the faces of people

Question 11

Fusiform gyrus

Answer 11

Contains the major face recognition area

Question 12

Strabismus in children

Answer 12

Leads to suppressed input from weak eye; results in abnormal development of the visual cortex

*Treat by patching the eye/surgically repairing it

Question 13

Retinal disparity

Answer 13

Mechanism for near-field perception

Question 14

Far-field depth perception

Answer 14

Depth cues are

Size
Interposition
Linear perspective
Light and shadow
Motion parallax

Question 15

LGN blood supply

Answer 15

Anterior choroidal artery

Question 16

Second Major Visual Pathway

Answer 16

RGCs project to the superior colliculus

=>Pulvinar

=>Finally, extrastriate visual areas

Question 17

Lesion in Area 18

Answer 17

Visual agnosia

Question 18

Simple Cells

Answer 18

Found in Layer IVCa; oval shaped “on” and “off” areas

*Orientation selective