Differentiate the dorsal ('where/how') visual stream from the ventral ('what') stream, including primary cortical areas and typical deficits.

Differentiate the dorsal ('where/how') visual stream from the ventral ('what') stream, including primary cortical areas and typical deficits.

• A. Dorsal stream processes spatial location and action guidance; ventral stream processes object identity; lesions cause optic ataxia for dorsal, visual agnosia for ventral.
• B. Dorsal stream processes color; ventral stream processes motion; lesions cause color blindness for dorsal, motion blindness for ventral.
• C. Dorsal stream is in the occipital lobe; ventral stream is in the frontal lobe; lesions cause aphasia for dorsal, agnosia for ventral.
• D. Dorsal stream handles language; ventral handles memory; lesions cause aphasia for dorsal, amnesia for ventral.

Answer: (A)

Two visual pathways handle different jobs in vision. The dorsal stream runs from the primary visual areas into the parietal cortex, including MT/V5 and posterior parietal regions, and it encodes where objects are in space and how to interact with them—guiding movements like reaching and grasping. The ventral stream travels from the same early areas into the inferior temporal cortex (through V4) and is responsible for identifying objects—recognizing what they are, along with color and form. When the dorsal stream is damaged, visuomotor coordination suffers even if basic vision remains intact, producing optic ataxia—trouble reaching for or grasping objects under visual guidance. When the ventral stream is damaged, object recognition is impaired, leading to visual agnosia—an inability to identify or name objects despite seeing them clearly. These deficits align with the idea that the dorsal pathway is about location and action, while the ventral pathway is about object identity.

Two visual pathways handle different jobs in vision. The dorsal stream runs from the primary visual areas into the parietal cortex, including MT/V5 and posterior parietal regions, and it encodes where objects are in space and how to interact with them—guiding movements like reaching and grasping. The ventral stream travels from the same early areas into the inferior temporal cortex (through V4) and is responsible for identifying objects—recognizing what they are, along with color and form.

When the dorsal stream is damaged, visuomotor coordination suffers even if basic vision remains intact, producing optic ataxia—trouble reaching for or grasping objects under visual guidance. When the ventral stream is damaged, object recognition is impaired, leading to visual agnosia—an inability to identify or name objects despite seeing them clearly. These deficits align with the idea that the dorsal pathway is about location and action, while the ventral pathway is about object identity.