Extrastriate cortex

The extrastriate cortex is a region of the visual cortex in the brain that is located adjacent to the primary visual cortex (V1). It encompasses several distinct areas, each of which is involved in processing different aspects of visual information. The extrastriate cortex includes areas such as V2, V3, V4, and V5/MT, among others.

Anatomy and Function

The extrastriate cortex is part of the occipital lobe and extends into the temporal lobe and parietal lobe. It is involved in higher-order processing of visual stimuli, including the perception of color, motion, and form. Each area within the extrastriate cortex has specialized functions:

• V2 (secondary visual cortex): Processes information from V1 and sends it to other extrastriate areas. It is involved in the integration of visual information.
• V3 (third visual complex): Involved in the processing of dynamic form and motion.
• V4 (fourth visual complex): Primarily involved in color perception and form recognition.
• V5/MT (middle temporal area): Specialized for motion detection and the perception of movement.

Connections

The extrastriate cortex receives input from the primary visual cortex and sends output to various regions of the brain, including the inferotemporal cortex and the posterior parietal cortex. These connections are crucial for the integration of visual information with other sensory modalities and for guiding motor actions based on visual input.

Clinical Significance

Damage to the extrastriate cortex can result in various visual deficits, depending on the specific area affected. For example:

• Lesions in V4 can lead to achromatopsia, a condition characterized by the inability to perceive color.
• Damage to V5/MT can result in akinetopsia, a rare disorder where the patient cannot perceive motion.

Research and Studies

The extrastriate cortex has been extensively studied using techniques such as functional magnetic resonance imaging (fMRI) and electrophysiology. These studies have provided insights into the functional organization of the visual system and the neural mechanisms underlying visual perception.

See Also

• Primary visual cortex
• Visual system
• Occipital lobe
• Temporal lobe
• Parietal lobe
• Achromatopsia
• Akinetopsia