The Striate cortex is thinner in layers containing output neurons that communicate with other parts of the brain. The striate cortex starts the processing of visual input. About a dozen additional areas of the human cerebral cortex participate in visual processing. They are often referred to as extrastriate areas or secondary visual cortex. Next to the striate cortex is an area known as V2, made of alternating thick and thin stripes separated by interstripe regions.
The thick stripes form the magnocellular pathway and project to a visual pathway known as the dorsal stream, referred to as the “where” pathway. The dorsal stream travels from the primary visual cortex to the parietal lobe then to the medial temporal lobe. The dorsal stream specializes in the analysis of movement.
The primary visual cortex V1 is the koniocortex, which is a sensory type. The lateral geniculate nucleus (LGN) receives visual information from retinal ganglion cells and sends most projections to the primary visual cortex (striate cortex, V1). Visual area V2 is the second major area in the visual cortex and the first region within the visual association area. Visual area V2 receives most of the V1 output and sends strong connections to V3, V4, and V5. The lateral geniculate nucleus not only provides feed-forward input to V1 but also receives robust feedback from V2 and extrastriate visual cortical areas.
The ventral stream known as the “What Pathway” begins with V1, goes through visual area V2, then through visual area V4, and to the inferior temporal cortex; it is associated with form recognition, object representation, and storage of long-term memory. Neurons in the visual cortex pass on action potentials after visual stimulation within their receptive field, which property is known as tuning.
