Repetitive transcranial magnetic stimulation (TMS) for 1 s at 4 Hz and 150% of the individual motor threshold was applied to primary motor cortex and adjacent cortical regions where no motor response could be produced. The hemodynamic reaction was measured using an event-related functional magnetic resonance setup. While all volunteers showed a typical signal increase beneath the coil during motor cortex stimulation, no consistent signal changes were present during frontal or parietal stimulation apart from activation of auditory cortex. The results suggest that neuronal stimulation by TMS is followed by an inhibitive phase that compensates for the effect of an initial neuronal activation. It is further concluded that the signal increases during motor cortex fit a sensory feedback from the moving body parts.
Copyright 2002 Elsevier Science Ireland Ltd.