V

V 1 Variable stimulus (also v). 2 Variance. 3 Photopic luminosity coefficient

V1, V2 ...V5 The V stands for vision and the number denotes a neuroanatomically distinct area of the visual system. See following for details

V1 The area of the occipital region also known as the primary visual cortex. Information arrives here from the lateral geniculate nucleus and is transmitted to other visual areas, primarily V2, V4, and V5, through different neural streams. The dorsal stream, often oversimplified as the 'where' pathway, goes through V2 to V5 and to the inferior parietal lobule and is linked with object location, motion and the processing of visual information for controlling movement. The ventral stream, somewhat simplistically called the 'what' pathway, also carries information to V2 then to V4 and the inferior temporal lobe and is associated with form and object recognition and long-term memory. V1 is the evolutionarily oldest visual area, the most extensively studied and the best understood. It is keyed to processing information about objects, both stationary and moving and carries out basic pattern recognition functions. In all animals with a V1, there is a clear correspondence between a specific spot in the visual field and a specific cortical location. Also known by a host of other names including retinotectal projection area, retinal projection area, and (sometimes ambiguously) visual projection area.

V2 An area of the occipital region that lies adjacent and anterior to V1. It receives inputs directly from V1 and sends information on to V3, V4, and V5. It also has feedback loops to V1. Anatomically it is split into four quadrants which function visuotopically (see retinotopic representation) to provide a full representation of the external, visual world.

V3 A part of the visual cortex. It is less well defined anatomically than other areas and is the only visual area that V1 does not project to. It lies just in front of V2, from which it receives inputs. It appears to have color sensitive neurons and may play a role in perception of global motion, a fact that suggests that it may have, like V2, a full representation of the visual world.

V4 An area of visual cortex that lies in the occipitotemporal cortex, anterior to V2. It receives inputs from V1 and V2 and processes information about color, spatial orientation, spatial frequency and geometric shapes. Most of what is known about it comes from work with macaques.

V5 The part of the visual cortex located in the extrastiate cortex of the medial temporal area. Projections come from V1, V2 and, probably, from V3; it transmits information to a wide variety of brain regions through a complex array of pathways. Its functions appear complex although there is compelling evidence for a primary role in processing movement. Lesions here cause a motion agnosia.

V¹ Scotopic luminosity coefficient. var., V¹.

v 1 Variable stimulus (also V). 2 Volume. 3 Volt.

vaccinate To produce immunity to a disease by inoculation.

vacuum activity An ethological term referring to the occurrence of a fixed action pattern in the absence of its usual external stimulus (or releaser). The assumption is that action-specific energy builds up, breaks through the inhibit