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A 2-D model of cortical sensory homunculus. A cortical homunculus (from Latin homunculus 'little man, miniature human' [1] [2]) is a distorted representation of the human body, based on a neurological "map" of the areas and portions of the human brain dedicated to processing motor functions, and/ or sensory functions, for different parts of the body.
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 ...
This is most commonly described in people that have undergone amputations in hands, arms, and legs, but it is not limited to extremities. The phantom limb feeling, which is thought [3] to result from disorganization in the brain map and the inability to receive input from the targeted area, may be annoying or painful. Incidentally, it is more ...
Wilder Penfield, a neurosurgeon, was one of the first to map the cortical maps of the human brain. [3] When performing brain surgeries on conscious patients, Penfield would touch either a patient's sensory or motor brain map, located on the cerebral cortex, with an electric probe to determine if a patient could notice either a specific sensation or movement in a particular area on their body.
In a number of cases, brain areas are organized into topographic maps, where adjoining bits of the cortex correspond to adjoining parts of the body, or of some more abstract entity. A simple example of this type of correspondence is the primary motor cortex, a strip of tissue running along the anterior edge of the central sulcus .
Somatosensory mapping involves measuring electrical responses on the surface of the brain as the result of the stimulation of peripheral nerves, such as mechanoreceptors that respond to pressure on the skin, and stimulating the brain directly to map sensory areas. Sensation has been tested in patients through the stimulation of the postcentral ...
Unlike the topographic maps of the senses, the neurons of the motor cortex are efferent neurons that exit the brain instead of bringing information to the brain through afferent connections. The motor system is responsible for initiating voluntary or planned movements ( reflexes are mediated at the spinal cord level, so movements that ...
Language areas are represented unilaterally in the human brain. [3] In around 95% of right-handers, these brain areas are often located on the left hemisphere, however the proportion reduces in left handers down to around 70%. [2] Therefore 7 in every 100 individuals is right-hemisphered for language and left-hand dominant. [4]