Functional MRI of cortical activations induced by transcranial magnetic stimulation (TMS)

The effects of repetitive transcranial magnetic stimulation (rTMS) on human brain activity and associated hemodynamics were investigated by blood-oxyg enation-level-dependent (BOLD) MRI using echo-planar imaging at 2.0 T. Apar t from bilateral activation of the auditory cortex by the audible rTMS disc harges (23 bursts, 1 s duration, 10 Hz, 10-20 s interstimulus intervals), B OLD responses were restricted to cortical representations of actual finger movements performed either voluntarily or evoked by suprathreshold rTMS of the motor cortex. Neither subthreshold rTMS of the motor cortex nor suprath reshold rTMS of the lateral premotor cortex induced a detectable BOLD respo nse. These findings suggest that neuronal depolarization as induced by rTMS modulates the spiking output of a brain area but does not automatically al ter cerebral blood flow and oxygenation. The observation of BOLD MRI activa tions probably reflects the afferent intracortical processing of real movem ents. (C) 2001 Lippincott Williams & Wilkins.