Cortical Homunculus

motor cortex

A cortical [kawr-ti-kuhlhomunculus [huh-muhng-kyuh-luhs] is a pictorial representation of the size of the brain areas for various parts of human anatomy. It is a visual representation of the concept of ‘the body within the brain’ that one’s hand or face exists as much as a series of nerve structures or a ‘neuron concept’ as it does a physical form. This concept relates to many neuro-biological phenomena including ‘phantom limb’ and ‘body integrity identity disorder’ (a psychological disorder wherein sufferers feel they would be happier living as an amputee).

There are two types of homunculus: sensory and motor. Each one shows a representation of how much of its respective cortex innervates certain body parts. The reason for the bizarre, distorted appearance of the homunculus is that the amount of cerebral tissue or cortex devoted to a given body region is proportional to how richly innervated and sensitive, or the number of muscles and motor units within that region is, not to its size. The resulting image is a grotesquely disfigured human with disproportionately huge hands, lips, and face in comparison to the rest of the body.

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