V3A

V3A is a visual area in the primate visual cortex. In humans and other primates it is part of the extrastriate cortex, located in the dorsolateral occipital region near areas V3 and MT/V5. It is named for its position in the visual area map and is considered part of the dorsal visual stream involved in spatial vision.

Anatomy and mapping: V3A exhibits retinotopic organization, with receptive fields that increase in size with eccentricity. Its borders are defined variably across studies, but it is typically situated medial to MT/V5 and lateral to early visual areas, receiving inputs from V1, V2, and V3 and projecting to MT/V5 and posterior parietal regions.

Function: Neurons in V3A respond to motion and binocular depth cues, contributing to the perception of three-dimensional structure from motion and disparity. The area is also implicated in processing complex shapes and orientation, supporting the dorsal stream’s roles in spatial localization and motion analysis.

Connectivity: V3A receives feedforward signals from early visual areas and communicates with MT/V5 and parietal areas, enabling integration of motion, depth, and form information for guiding perception and action.

Research and notes: V3A is routinely identified in functional retinotopy studies in humans, though exact boundaries and functional specialization can vary across individuals. In macaques, the homologous area shows similar but not identical organization, reflecting species differences in cortical mapping.

See also: visual cortex areas, V3, MT/V5, dorsal stream.