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The primary visual cortex (usually called V1) is the most well-studied visual area in the brain. It is also the simplest and first cortical visual area. Situated around the calcarine sulcus in the occipital lobe, it is the most caudal structure in the brain. It receives signals relayed from the retina via the lateral geniculate nucleus of the thalamus. Thus, primary visual cortex is only one synapse away from the retina.

The functionally defined primary visual cortex is equivalent to the anatomically defined striate cortex. The name "striate cortex" is derived from the highly visible striations (stripes) that are made up of the prominent somas of neurons in layer 4 of the gray matter. The primary visual cortex is also anatomically equivalent to Brodmann area 17, or BA17. Brodmann areas are based on a histological map of the human brain created by Korbinian Brodmann.

1 History

David Hubel and Torsten Wiesel were the first scientists to show that primary visual cortex shows tuning for oriented lines. Supposedly they were presenting visual stimuli on slides to a catFor alternative meanings see cat (disambiguation). The cat (also called domestic cat or house cat is a small feline carnivorous mammal. Its scientific name is Felis silvestris catus or Felis silvestris domesticus but the species is sometimes referred to a while recording neural signals. They were unable to find any stimulus that would make the cell fire until they presented a slide which had a crack on it. Although they won the Nobel PrizeThe Nobel Prizes (pronounced no-BELL or no-bell are awarded annually to people who have done outstanding research, invented groundbreaking techniques or equipment, or made outstanding contributions to society. It is generally regarded as the supreme comme in medicine for later work, it is this discovery for which they are most famous today.

During the 1970s, there was a major debate about the function of primary visual cortex - whether it was a feature detector or a local band-limited Fourier filter. Most scientists today accept the latter hypothesis.

During the 1980s, there was a major debate about the relationship between functional specialization within V1, the magnocellular and parvocellular pathways of the retina and lateral geniculate nucleus, and the dorsal streamWhere It Is The dorsal stream (also known as the parietal stream or the where stream) stretches from the primary visual cortex (V1) in the occipital lobe forward into the parietal lobe. It is interconnected with the parallel ventral stream (the what strea and ventral streamThe primate visual system consists of about thirty areas of the cerebral cortex called the visual cortex. The visual cortex is divided into the ventral stream and the dorsal stream. The ventral stream is associated with object recognition and form represe. Most scientists today believe that evidence for this hypothesis is weak.

2 Current Research

Most research on the primary visual cortex involves recording action potentialelectrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. As the traveling signals of nerves and as the localized changes that contract muscle cells, action potentials are as from electrodes with the brain of catFor alternative meanings see cat (disambiguation). The cat (also called domestic cat or house cat is a small feline carnivorous mammal. Its scientific name is Felis silvestris catus or Felis silvestris domesticus but the species is sometimes referred to as, ferrets, or monkeys. Other scientists have studied primary visual cortex by recording intrinsic optical signals and fMRI signals from v1.

One recent discovery about v1 is that metabolic signals measured by fMRI show very large attentional modulation. This result strongly contrasts with macaque physiology research showing very small changes (or no changes) in firing associated with attentional modulation.

Other current work on v1 seeks to fully characterize its tuning properties, and to use it as a model area for the canonical cortical circuit.

Lesions to primary visual cortex usually lead to a scotoma, or hole in the visual field. Interestingly, patients with scotomas are often able to make use of visual information presented to their scotomas, despite being unable to consciously perceive it. This phenomenon, called blindsight, is widely studied by scientists interested in the neural correlate of consciousness.

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