title: Repeated premotor rTMS leads to cumulative plastic changes of motor cortex excitability in humans.
abstract: We explored the aftereffects of two premotor 1 Hz rTMS sessions on motor cortex excitability in healthy humans. In experiment 1, 11 healthy right-handed volunteers received 20-min submotor threshold 1 Hz rTMS trains over the left premotor cortex on 2 consecutive days. Left motor cortex excitability was determined at baseline, immediately after, 30, 60, 120 min, and 24 h after each rTMS session. We measured motor thresholds, amplitudes of motor-evoked potentials, silent periods, and paired-pulse excitability at interstimulus intervals (ISI) of 3-7, 10, and 15 ms. In experiment 2, 5 volunteers received two identical rTMS trains on Days 1 and 7. Measurements were carried out on Day 1 (first rTMS train), Day 2, and Day 7 (second rTMS train). In experiment 1 there was a selective increase of paired pulse facilitation at an ISI of 7 ms after rTMS lasting for less than 30 min on Day 1. This effect was also present after rTMS on Day 2. However, it persisted for at least 2 h. In experiment 2 the same extra facilitation was induced by rTMS on Days 1 and 7 but not on Day 2. It lasted for less than 30 min on both Day 1 and Day 7. We conclude that 1 Hz premotor rTMS leads to cumulative plastic changes of intrinsic motor cortex excitability when repeated within 24 h but not after 1 week, implying the formation of memory after the first rTMS train lasting more than a day but less than a week.
authors.affiliation: Department of Neurology, University of Hamburg, Hamburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bäumer
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Lange
authors.forename: Joachim
authors.initials: J
authors.lastname: Liepert
authors.forename: Cornelius
authors.initials: C
authors.lastname: Weiller
authors.forename: Hartwig R
authors.initials: HR
authors.lastname: Siebner
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
authors.forename: Alexander
authors.initials: A
authors.lastname: Münchau
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004574:Electromagnetic Fields; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D009415:Nerve Net / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*