Somatosensory System - Anatomy - Brain

Brain

The primary somatosensory area in the human cortex (also called primary somatic sensory cortex or SI) is located in the postcentral gyrus of the parietal lobe and makes up four distinct fields or regions known as Brodmann area 3a, 3b, 1, and 2. The postcentral gyrus is the location of the primary somatosensory area, the main sensory receptive area for the sense of touch. Any individual neuron has its receptive field on the skin.

A relationship between the somatosensory cortical areas and their projection of the body was discovered by recording electrical activity in the human cortex after mechanosensory stimulation of different body parts during neurosurgical procedures. These data led to the construction of somatotopic maps in which a Somatotopic arrangement was generated. Like other sensory areas, there is a map of sensory space called a homunculus at this location. For the primary somatosensory cortex, this is called the sensory homunculus. Areas of this part of the human brain map to certain areas of the body, dependent on the amount or importance of somatosensory input from that area. For example, there is a large area of cortex devoted to sensation in the hands, while the Human back has a much smaller area. Somatosensory information involved with proprioception and posture also targets an entirely different part of the brain, the cerebellum.