Higher order visual processing

What is the ventral pathways responsible for

Form and colour processing - identifying ‘what’ the object is

Where does the ventral pathway project to

From V1 to The inferior temporal lobe (IFC)

What is the dorsal pathways responsible for?

Motion, spatial location and perception in low light - identifying ‘where’ the object is

Where does the dorsal pathway project to?

The posterior parietal cortex

What types of V1 pathways project to V2 stripes

V2 has thick, thin and interstrip regions

blobs in V1 → thin stripes

interblobs in V1 → thick stripes

segregation of pathways is maintained in V2

What do the parvo, magno and koniceullar channels form in V2

Magnocellular (4ca) → motion/where pathway

Parvocellular (4Cb) and Koniocellular (blobs) → colour'/what pathway

What is V2 cortex known as

Pre-striate cortex/ Brodmann area 18

How is visual space represented in V2

as a complete topographic map, preserving spatial relations from V1

What are V2 cells sensitive to

Orientation, spatial frequency (motion) and colour

How many times are V2 receptive fields larger than V1

they are 2/3 times larger

What is V3A primarily involved in

Coherent motion and depth - part of the dorsal stream

• thick stripes in V2 project to dorsal of V3

What is V3 more focused on

shape and form - part of the ventral stream (blobs in v1 project to interstripes in V2 then project toV3)

what does the MT/V5 do?

processes motion direction - requires moving stimuli for activation

what can damage to MT/V5 cause

Akinetopsia (motion blindness)

What does MST (medial superior temporal) process?

Linear motion, radial motion and circular motion → supports navigation and motion perception

• more complex as not just direction but complex understanding as where object is moving

What is the role of the area v4 (parvocellular) in the visual system

Ventral stream: receives input from blobs and regions of the striate cortex

• colour processing, orientation and object sensitivity, summation of edges and corners (summate several V2 and V1 neurons)

What can lesions in the V4 lead to

Achromatopsia (partial or full colour blindness)

How does V4 differ from V1

V4 has larger receptive fields and is sensitive to geometric features

What is the key functional difference between V4 and V5

V4 is slower and processes colour whereas V5 processes motion quicker

Why does visual processing increase in complexity as you go from V1 to V5/V4

Due to summation and integration of receptive fields - a hierarchal structure

What would happen if you had lesions in V1

complete visual loss as not further projections to V2