What Is Motor and Sensory Homunculus?

Motor and sensory homunculus is a map on the surface of the brain for motor and sensory inputs from the body. The sensorimotor homunculus is also often depicted as a figure of a man, with the size of parts of his body corresponding to the relative areas these parts have on the surface of the cortex.

The motor area, located at the back of the frontal lobes of the brain, controls voluntary movement. Adjacent to this area of the brain is the sensory area in the parietal lobe. This area is responsible for receiving signals related to touch, pain and temperature. Large areas of the brain surface in the middle correspond to the head and hands. The rest of the body is on the edges of this map.

The smaller the movement a person wants to make, the more work for the brain. The result of this is that in the homunculus represented as a human body, the lips and hands are particularly large relative to other parts of the body, and feet are disproportionately big as well.

The homunculus is linked to the issue of phantom limbs which is a perceived sensation from the fingers or whole limbs that have been amputated. The adult brain is not hard-wired, but can re-map. The signal originating at a point between the amputated limb and the homunculus will generate a sensation in the homunculus where the amputated limb was.