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In neuroanatomy, the primary somatosensory cortex is located in the postcentral gyrus of the brain's parietal lobe, and is part of the somatosensory system. It was initially defined from surface stimulation studies of Wilder Penfield , and parallel surface potential studies of Bard, Woolsey, and Marshall.
Although initially defined to be roughly the same as Brodmann areas 3, 1, and 2, more recent work by Kaas has suggested that for homogeny with other sensory fields only area 3 should be referred to as "primary somatosensory cortex", as it receives the bulk of the thalamocortical projections from the sensory input fields [citation needed].
The term primary comes from the fact that these cortical areas are the first level in a hierarchy of sensory information processing in the brain. This should not be confused with the function of the primary motor cortex, which is the last site in the cortex for processing motor commands. [1]
The postcentral gyrus is in the parietal lobe and its cortex is the primary somatosensory cortex (Brodmann areas 3, 2 and 1) collectively referred to as S1. BA3 receives the densest projections from the thalamus. BA3a is involved with the sense of relative position of neighboring body parts and amount of effort being used during movement.
This cortex is typically represented as a sensory homunculus which orients the specific body parts and their respective locations upon the homunculus. Areas such as the appendages, digits, penis, [2] and face can draw their sensory locations upon the somatosensory cortex. The areas which are finely controlled (e.g., the digits) have larger ...
An example is the somatosensory map which is a projection of the skin's surface in the brain that arranges the processing of tactile sensation. This type of somatotopic map is the most common, possibly because it allows for physically neighboring areas of the brain to react to physically similar stimuli in the periphery or because it allows for ...
The corticospinal tract is a white matter motor pathway starting at the cerebral cortex that terminates on lower motor neurons and interneurons in the spinal cord, controlling movements of the limbs and trunk. [1] There are more than one million neurons in the corticospinal tract, and they become myelinated usually in the first two years of life.
In humans, brain activity consistent with that of mirror neurons has been found in the premotor cortex, the supplementary motor area, the primary somatosensory cortex, and the inferior parietal cortex. [8] The function of the mirror system in humans is a subject of much speculation.