Visual area V3

See:Visual cortex for overview of complete visual area of the brain

Visual area V3 is a term used to refer to the region of cortex located immediately in front of V2. To date, some controversy exists regarding the exact extent of this area, with some researchers proposing that this is in fact a complex of two or three functional subdivisions. For example, David Van Essen and others (1986) have proposed that the existence of a "dorsal V3" in the upper part of the cerebral hemisphere, which is dinstinct from the "ventral V3" (or ventral posterior area, VP) located in the lower part of the brain. Dorsal and ventral V3 have distinct connections with other parts of the brain, appear different in sections stained with a variety of methods, and contain neurons that respond to different combinations of visual stimulus (for example, colour-selective neurons are more common in the ventral V3).

Dorsal V3 is normally considered to be part of the dorsal stream, receiving inputs from V2 and from the primary visual area and projecting to the posterior parietal cortex. It may be anatomically located in Brodmann area 19. Debate exists as to whether there are also adjacent areas 3A and 3B. Recent work with fMRI has suggested that area V3/V3A may play a role in the processing of global motion Other studies prefer to consider dorsal V3 as part of a larger area, named the dorsomedial area (DM), which contains a representation of the entire visual field. Neurons in area DM respond to coherent motion of large patterns covering extensive portions of the visual field (Lui and collaborators, 2006).

Ventral V3 (VP) has much weaker connections from the primary visual area, and stronger connections with the inferior temporal cortex. While earlier studies proposed that VP only contained a representation of the upper part of the visual field (above the point of fixation), more recent work indicates that this area is more extensive than previously appreciated, and like other visual areas it may contain a complete visual representation. The revised, more extensive VP is referred to as the ventrolateral posterior area (VLP) by Rosa and Tweedale (2000).

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