Stephani C; Paulus W; Sommer M. Institution Stephani,Caspar. Department of Clinical Neurophysiology, Universi ty of Gottingen, Gottingen, Germany email@example.com. Paulus,Walter. Department of Clinical Neurophysiology, Universi ty of Gottingen, Gottingen, Germany. Sommer,Martin. Department of Clinical Neurophysiology, University of Gottingen, Gottingen, Germany.
The effect of current flow direction on motor hot spot allocation by transcranial magnetic stimulation.
Source: Physiological Reports. 4(1), 2016 Jan.
Abstract: The objective of this study was to investigate the signifi cance of pulse configurations and current direction for corticospinal acti vation using transcranial magnetic stimulation (TMS). In 11 healthy subjects (8 female), a motor map for the motor evoked potentials (MEPs) reco rded from the first dorsal interosseus (FDI), abductor digiti minimi (ADM), extensor carpi radialis, and biceps brachii (BB) muscles of the domi nant side was established. Starting from a manually determined hot spot of the FDI representation, we measured MEPs at equal oriented points on an hexagonal grid, with 7 MEPs recorded at each point, using the follow ing pulse configurations: posteriorly directed monophasic (Mo-P), anter iorly directed monophasic (Mo-A), biphasic with the more relevant seco nd cycle oriented posteriorly (Bi-P) as well as a reversed biphasic cond ition (Bi-A). For each pulse configuration, a hot spot was determin ed and a center of gravity (CoG) was calculated. We found that the facto r current direction had an effect on location of the CoG-adjusted hot spo t in the cranio-caudal axis but not in the latero-medial direction with anteriorly directed pulses locating the CoG more anteriorly and vice versa. In addition, the CoG for the FDI was more laterally than the cort ical representations for the abductor digiti minimi (ADM) and ext ensor carpi radialis (ECR) which were registered as well. The results indi cate that direction of the current pulse should be taken into account f or determination of the motor representation of a muscle by TMS.
Co pyright © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.
Publication Type Journal Article.