Klinische Neurophysiologie 2008; 39 - A138
DOI: 10.1055/s-2008-1072940

Preceding repetitive stimulation diminishes long-term potentiation-like plasticity in human motor cortex

I Delvendahl 1, N Jung 1, M Cronjaeger 1, F Mainberger 1, N Kuhnke 1, P Nöllke 2, V Mall 1
  • 1Universitätsklinikum, Neuropädiatrie, Freiburg
  • 2Universitätsklinikum, Freiburg

Introduction: Neuronal networks undergo plastic changes considered essential for learning and memory. Long-term potentiation (LTP) and long-term depression (LTD) are able to account for these changes in vitro and underlie the rules proposed by the Bienenstock-Cooper-Munro (BCM) theory of bidirectional plasticity.

Methods: We tested whether the history of previous excitation as part of the BCM theory has an influence on the induction of increased cortical excitability with paired associative stimulation (PAS). A PAS25ms protocol was preceded with repetitive transcranial magnetic stimulation (rTMS) at 0.1Hz which alone does not have any effect on excitability.

Results: Motor-evoked potential (MEP) amplitudes from the left abductor pollicis brevis muscle did increase significantly from 1.04±0.14 mV to 1.78±0.66 mV when PAS alone was applied (p=0.008) but did not increase when PAS was preceded with rTMS at 0.1Hz (1.14±0.23 mV to 1.14±0.76 mV).

Discussion: A stable LTP-like effect diminishes when rTMS at 0.1Hz is conducted before PAS. These results are in accordance to the BCM theory stating that plasticity depends on the history of previous excitation. Furthermore, this effect might contribute to variability experienced with PAS.