Cortical homunculus

A cortical homunculus () is a distorted representation of the human body, based on a neurological "map" of the areas and proportions of the human brain dedicated to processing motor functions, or sensory functions, for different parts of the body. Nerve fibresconducting somatosensory information from all over the bodyterminate in various areas of the parietal lobe in the cerebral cortex, forming a representational map of the body. Findings from the 2010s and early 2020s began to call this interpretation into question, and research is ongoing in this field. A motor homunculus represents a map of brain areas dedicated to motor processing for different anatomical divisions of the body. The primary motor cortex is located in the precentral gyrus, and handles signals coming from the premotor area of the frontal lobes. A sensory homunculus represents a map of brain areas dedicated to sensory processing for different anatomical divisions of the body. The primary sensory cortex is located in the postcentral gyrus, and handles signals coming from the thalamus. The thalamus itself receives corresponding signals from the brain stem and spinal cord. Along the length of the primary motor and sensory cortices, the areas specializing in different parts of the body are arranged in an orderly manner, although ordered differently than one might expect. The toes are represented at the top of the cerebral hemisphere (or more accurately, "the upper end," since the cortex curls inwards and down at the top), and then as one moves down the hemisphere, progressively higher parts of the body are represented, assuming a body that is faceless and has arms raised. Going further down the cortex, the different areas of the face are represented, in approximately top-to-bottom order, rather than bottom-to-top as before. The homunculus is split in half, with motor and sensory representations for the left side of the body on the right side of the brain, and vice versa.