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

Abstract

Plastic changes of neuronal networks are considered essential for learning and memory. Synaptic plasticity in vitro in form of long-term potentiation underlies the rules of the Bienenstock-Cooper-Munro theory of bidirectional plasticity. In this study we asked whether LTP-like plasticity in human motor cortex induced and evaluated by transcranial magnetic stimulation (TMS) is in accordance with the BCM theory. We therefore preceded paired associative stimulation (PAS) with repetitive transcranial magnetic stimulation (rTMS, f=0.1Hz). Amplitudes of motor-evoked potentials (MEP) showed a significant increase from 1.04±0.14 mV to 1.95±0.44 mV (p=0.005), when PAS alone was applied. In contrast, no increase was measured when rTMS was carried out before PAS (1.14±0.23 mV to 0.83±0.61 mV, p=0.668).