Big Picture: Funny little man, seriously big points

This grotesque figure is the homunculus ('little man' in Latin). The graphical representation of how the cortex is devoted to different areas of the body, first drawn by Canadian neurosurgeon Wilder Penfield in the 1940s, has become a classic example of topographic mapping. It has been used as a model of plasticity, and of self-organisation in neural systems, but even now it is not fully understood.

Francis McGlone, Professor of Cognitive Neuroscience at Liverpool John Moores University, has big questions for the little man. 'Why are hands next to mouth, and feet next to genitals? Martha Farah at the University of Pennsylvania thinks it's due to the mechanisms of self-organisation in combination with the flexed posture of the limbs in the fetal position. And why is it always the hom-unculus and not the her-munculus?'

Professor McGlone is particularly interested in what alternatives would look like. 'The homunculus is a map of the sensory body. What would a map of the sensuous body look like, and where would it be located? Is there a pleasure hom/hermunculus lurking somewhere?'

Recent research from Professor McGlone's group has identified a system of nerves in the skin that love to be stroked – sensuously! 'When body sites such as the face, the arms and the torso are gently stroked, people report different levels of pleasure depending on where they are touched. Interestingly, for the "self-touchers" amongst us, these "pleasure nerves" are not found in the palmar skin of the hand, so when touching oneself it's as if the sensory hand were exciting the sensuous body! Tickling its fancy…'

As for the genitalia, Professor McGlone says they are 'all over the place, depending on which version of the "little man" you are looking at. And even those few studies that have tried to locate them in the "little woman" cannot agree where they are! Sound familiar?'

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