Input-output organization of the foot motor area in humans

Objective: A well-organized input-output relation similar to that of the mo nkey motor cortex has been demonstrated in the human hand motor area (Terao Y, Ugawa Y, Uesaka Y, Hanajima R, Gemba-Shimizu K, Ohki Y, Kanazawa I. Inp ut-output organization in the hand area of the human motor cortex, Electroe nceph clin Neurophysiol 1995;97:375-381). The aim of this study is to inves tigate the input-output organization of the human foot motor area. Methods: We studied the effect of tactile stimuli given to the toe tip on t he sizes of following responses; motor evoked potentials (MEPs) elicited by transcranial magnetic or electrical stimulation (TMS or TES) over the moto r cortex and magnetic stimulation at the foramen magnum level. Results: Air stimuli applied to the toe tip facilitated magnetically evoked MEPs of mainly the muscle attached to that toe, although a less prominent facilitation was also noted in muscles attached to the adjacent toes. Neith er responses evoked by TES, nor those by stimulation at the foramen magnum level, were affected by air stimuli. These results suggest that the observe d facilitatory effect occurs at the cortical level. Conclusion: A fairly well-organized input-output relation is present also i n the foot motor area in humans, although the facilitatory effect is not so topographically restricted as is noted for the hand motor area. (C) 1999 E lsevier Science Ireland Ltd. All rights reserved.