Postcentral gyrus

Gray726 — Gray's FIG. 726– Lateral surface of left cerebral hemisphere, viewed from the side.

The lateral postcentral gyrus is a prominent structure in the parietal lobe of the human brain and 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.

Postcentral gyrus[]

The lateral postcentral gyrus is bounded by:

medial longitudinal fissure medially (to the middle)
central sulcus rostrally (in front)
postcentral sulcus caudally (in back)
lateral sulcus inferiorly (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 homunculus in this location. For the primary sensory areas, this is called the sensory homunculus. See a somewhat fanciful and highly schematic representation of the sensory homunculus at lower right.

Brodmann areas 3, 1 and 2[]

Ba1 2 3 — Brodmann areas 3, 1 and 2 of human brain. Brodmann area 3 is in red, area 1 in green, and area 2 in yellow.

Brodmann areas 3, 1 and 2 comprise the primary somatosensory cortex of the human brain. Because Brodmann sliced the brain somewhat obliquely, he encountered area 1 first; however, from rostral to caudal the Brodmann designations are 3, 1 and 2, respectively.

Homunculus sensory — Sensory homunculus of the human brain.

This area of cortex, as shown by Wilder Penfield and 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 cortex are devoted to processing information from these areas.

These areas contain cells that project to the secondary somatosensory cortex.