Low-frequency rTMS over lateral premotor cortex induces lasting changes in regional activation and functional coupling of cortical motor areas

Objective: To study the effect of 0.9 Hz repetitive transcranial magnetic stimulation (rTMS) of the lateral premotor cortex on neuronal activity in cortical motor areas during simple motor tasks. Methods: In 8 subjects, electroencephalogram (EEG) and electromyogram (EMG) were simultaneously recorded during voluntary contractions of the thumb before and after a 15 min train of 0.9 Hz rTMS over the left lateral premotor cortex at stimulus intensity of 90% of active motor threshold. After-effects on cortical motor activity were assessed by measuring the task-related EEG power and inter-regional coherence changes, and the EEG–EMG coherence (EMGCoh). Results: Low-frequency rTMS over the premotor cortex gave rise to (i) a reduction of the task-related power decrease in the alpha and beta bands, (ii) a selective increase in the task-related coherence change among cortical motor areas in the upper alpha band, and (iii) a decrease in the cortico-muscular coherence. These effects lasted about 15 min after the end of rTMS intervention. Conclusions: The attenuated task-related power changes and decreased EMGCoh point to a lasting suppression of voluntary activation of cortical motor areas after rTMS. The present data provide an evidence for a transient reorganization of movement-related neuronal activity in the cortical motor areas after 0.9 Hz rTMS over the premotor cortex. Significance: Low-frequency rTMS changes the regional activation and functional coupling of cortical motor areas as demonstrated by EEG analysis.