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The variability of intracortical inhibition and facilitation

Orth, M; Snijders, AH; Rothwell, JC; (2003) The variability of intracortical inhibition and facilitation. CLIN NEUROPHYSIOL , 114 (12) 2362 - 2369. 10.1016/S1388-2457(03)00243-8.

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Abstract

Objective: To assess the variability of transcranial magnetic stimulation paired pulse measurements of cortical excitability between subjects, between sessions and within subjects within sessions.Methods: In experiment 1, intracortical inhibition and facilitation were assessed with a fixed conditioning stimulus intensity (CSI) of 80% of active motor threshold (AMT) whereas in experiment 2, the effect of different CSIs (60-110% of AMT) was investigated.Results: Experiment 1 revealed that subjects differed significantly in the degree of inhibition and facilitation. Between sessions the variability was substantial as predicted by high within session variability. Experiment 2 allowed determination of individual thresholds for inhibition and facilitation. These thresholds were the best predictor of the amount of inhibition or facilitation at a given CSI. Across subjects we observed a high correlation of the threshold for inhibition (expressed in terms of maximum stimulator output) with AMT (r = 0.93). Results for facilitation were more variable.Conclusions: The variability was high if a single CSI was used to compare the percent intracortical inhibition or facilitation between subjects, or between sessions. Much less variable was the threshold for intracortical inhibition/facilitation, which was highly correlated to AMT. We suggest that the ratio of CSI:AMT is a robust and useful additional measure of the integrity of neuronal circuits underlying intracortical inhibition/facilitation. (C) 2003 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Type: Article
Title: The variability of intracortical inhibition and facilitation
DOI: 10.1016/S1388-2457(03)00243-8
Keywords: transcranial magnetic stimulation, paired pulse technique, variability, active motor threshold, inhibition threshold, facilitation threshold, HUMAN MOTOR CORTEX, STIMULATION
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Clinical and Movement Neurosciences
URI: http://discovery.ucl.ac.uk/id/eprint/69568
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