Chapter 6: Dorsal and Ventral Streams

Streams

pathways that conduct information from the primary visual cortex

Dorsal Stream

flows from the primary visual cortex to the dorsal prostrate cortex to the posterior parietal cortex

What does the dorsal stream respond to?

spatial stimuli (location of objects/direction of movement)

involved in perception of where objects are

Ventral Stream

flows from primary visual cortex to the ventral prostrate cortex to the inferotemporal cortex

What does the ventral stream respond to?

responds to the characteristics of objects, such as color and shape.

(faces, bodies, animals, letters, tools)

involved in the perception of what objects are.

Where vs. What Theory of Vision

damage to some areas of cortex may abolish certain aspects of vision while leaving others unaffected.

(Ungeidler and Mishkin)

Where would damage to the dorsal stream be?

posterior parietal cortex

What happens to someone when there is damage to the dorsal stream?

disrupts visual spatial perception (where objects are)

has difficulty reaching for objects they could easily describe

disrupts visually guided behavior but not conscious visual perception

Where would damage to the ventral stream be?

inferotemporal cortex

What happens to someone where there is damage to the ventral stream?

disrupts visual pattern recognition

has difficulty describing something but can easily reach for it

disrupts conscious visual perception but not visually guided behavior

Prospognosia

visual agnosia for faces

Agnosia

failure of recognition

Visual Agnosia

specific agnosia for visual stimuli, can see something but can't tell what it is

(damage to ventral stream)

Akinetopsia

can't see movement progress

damage to dorsal stream