. Every textbook on brain behaviour relationships has one oranother version of the famous motor ‘homunculus’ – the distortedbody part graphic drawn juxtaposed to the primary motor cortex. Themotor homunculus is based on Penfield’s groundbreaking work showingthat the amount of cortical area affecting movement of a given bodypart was not related to the body part’s size but to its motorcontrol capability (thus the grotesquely enlarged appearance of thehomunculus’ lips and hands). Penfield used short-durationelectrical pulses in the posterior region of the frontal lobe thatelicited, simple, nearly reflexive, twitch-like movements. Had hiselectrical stimulation been of much longer-duration, what type ofmovements would he have likely elicited from there?
