Rapid cortical motor output map changes assessed by the triple stimulationtechnique

THE amplitudes of motor evoked potentials (MEPs) were mapped by transcrania l magnetic stimulation (TMS) using the triple stimulation technique (TST) i n 11 normal individuals. Stimuli were given while the subjects were (a) dis tracted, (b) concentrating on their target (recorded) hand, and (c) concent rating on their contralateral hand. Within seconds, the proportion of excit ed motor units increased, similarly in all subjects, by an average of 70% f rom (a) to (b), and by 48% from (a) to (c). At the optimal stimulation site , results obtained with the TST were compared to those of conventional MEPs . The TST proved superior in detecting the rapid changes of the motor outpu t caused by the non-specific mental tasks studied. (C) 1999 Lippincott Will iams & Wilkins.