Question

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

Answer 1

The motor cortex comprises three different areas of the frontal lobe, primary motor cortex, the premotor cortex, and the supplementary motor area. Of the three motor cortex areas, stimulation of the primary motor cortex requires the least amount of electrical current to elicit a movement. Stimulation of premotor cortex or the supplementary motor area requires higher levels of current to elicit movements and often results in more complex movements than stimulation of the primary motor cortex. Low levels of brief stimulation typically elicit simple movements of individual body parts.

Neurons in primary motor cortex supplementary motor cortex and premotor cortex give rise to the fibres of the corticospinal tract. corticospinal l tract pathways coordinate head, neck and eye movements in response to visual targets. control coarse movements of the proximal muscles, and posture and balance.Motor cortex area controls the voluntary movements of the opposite side of the body.