- Postcentral gyrus
Name = Postcentral gyrus
Latin = gyrus postcentralis
GraySubject = 189
GrayPage = 823
Caption = Postcentral gyrus of the human brain.
Caption2 = Brodmann areas 3, 1 and 2 of human brain. Brodmann area 3 is in red, area 1 in green, and area 2 in yellow.
BrainInfoType = hier
BrainInfoNumber = 87
DorlandsPre = g_13
DorlandsSuf = 12405446
The lateral postcentral gyrus is a prominent structure in the
parietal lobeof the human brainand an important landmark. It was initially defined from surface stimulation studies of 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 received the bulk of the thalamocortical projection from the sensory input fields.
The lateral postcentral gyrus is bounded by:
medial longitudinal fissuremedially (to the middle)
central sulcusrostrally (in front)
postcentral sulcuscaudally (in back)
lateral sulcusinferiorly (underneath)
It is the location of
primary somatosensory cortex, the main sensory receptive area for the sense of touch. Like other sensory areas, there is a map of sensory space called a homunculusin this location. For the primary somatosensory cortex, this is called the "sensory homunculus". See a somewhat fanciful and highly schematic representation of the sensory homunculus below.
Brodmann areas 3, 1 and 2
Brodmann areas 3, 1 and 2 comprise the primary
somatosensory cortexof the human brain. Because Brodmann sliced the brainsomewhat obliquely, he encountered area 1 first; however, from rostralto caudalthe Brodmann designations are 3, 1 and 2, respectively.
This area of cortex, as shown by
Wilder Penfieldand others, has the pattern of a homunculus. That is, the legs and trunk fold over the midline; the arms and hands are along the middle of the area shown here; and the face is near the bottom of the figure. While it is not well-shown here, the lips and hands are enlarged on a proper homunculus, since a large number of neurons in the cerebral cortexare devoted to processing information from these areas.
These areas contain cells that project to the
secondary somatosensory cortex.
Lesions affecting the primary somatosensory cortex produce characteristic symptoms including:
agraphesthesia, astereognosia, loss of vibration, proprioceptionand fine touch(because the third-order neuron of the medial-lemniscal pathway cannot synapse in the cortex). It can also produce hemineglect, if it affects the non-dominant hemisphere.
It could also reduce
nociception, thermoceptionand crude touch, but since information from the spinothalamic tractis interpreted mainly by other areas of the brain (see insular cortexand cingulate gyrus), it is not as relevant as the other symptoms.
List of regions in the human brain
* - area 1
* - area 2
* - area 3
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