M Sommer1, T Wu, F Tergau, W Paulus. 1. Department of Clinical Neurophysiology, University of Goettingen, P.O. Box 3742, D-37070, Goettingen, Germany.
Abstract
OBJECTIVES: Repetitive transcranial magnetic stimulation (rTMS) can modify cortical excitability and is widely used for clinical and research purposes. We sought to determine the intra- and interindividual variability of its effects on motor cortex excitability, and whether repeated paired-pulses yield less variability than repeated single-pulses. METHODS: We investigated rTMS over the left motor cortex of 6 healthy subjects and recorded motor evoked potentials (MEPs) from the right abductor digiti minimi muscle. Eighty single suprathreshold stimuli or conditioning-test pairs of stimuli were delivered at 2Hz frequency. The pairs consisted of a subthreshold pulse followed by a suprathreshold pulse after 2, 5 or 10ms. In each subject we studied all types of rTMS 5 times on separate days. Single suprathreshold pulses at 0.17Hz preceded rTMS for baseline determination. RESULTS: The day-to-day variability of MEPs during either type of rTMS was small compared to the subject-to-subject variability. MEPs increased during all types of rTMS except for interstimulus interval (ISI) 2ms. Paired-pulses yielded less variability than single-pulse rTMS. CONCLUSIONS: Motor responses to rTMS show a high interindividual, but a low intraindividual variability. Repeated paired-pulses yield less variability than repeated single-pulses.
OBJECTIVES: Repetitive transcranial magnetic stimulation (rTMS) can modify cortical excitability and is widely used for clinical and research purposes. We sought to determine the intra- and interindividual variability of its effects on motor cortex excitability, and whether repeated paired-pulses yield less variability than repeated single-pulses. METHODS: We investigated rTMS over the left motor cortex of 6 healthy subjects and recorded motor evoked potentials (MEPs) from the right abductor digiti minimi muscle. Eighty single suprathreshold stimuli or conditioning-test pairs of stimuli were delivered at 2Hz frequency. The pairs consisted of a subthreshold pulse followed by a suprathreshold pulse after 2, 5 or 10ms. In each subject we studied all types of rTMS 5 times on separate days. Single suprathreshold pulses at 0.17Hz preceded rTMS for baseline determination. RESULTS: The day-to-day variability of MEPs during either type of rTMS was small compared to the subject-to-subject variability. MEPs increased during all types of rTMS except for interstimulus interval (ISI) 2ms. Paired-pulses yielded less variability than single-pulse rTMS. CONCLUSIONS: Motor responses to rTMS show a high interindividual, but a low intraindividual variability. Repeated paired-pulses yield less variability than repeated single-pulses.
Authors: Xiaoming Du; Fow-Sen Choa; Ann Summerfelt; Malle A Tagamets; Laura M Rowland; Peter Kochunov; Paul Shepard; L Elliot Hong Journal: Exp Brain Res Date: 2014-11-16 Impact factor: 1.972