Navigated transcranial magnetic brain stimulation: should the premotor cortex be stimulated for the mapping of the hand motor cortex?

Objective: Navigated magnetic brain stimulation (NBS) has become a valuable tool for mapping the motor cortex. Until now, the premotor cortex has not been regarded as a target for NBS mapping. Methods: 5 human right handed adults were studied, 4 of which harbored a unilateral brain tumor. We used NBS for mapping of the precentral gyrus and premotor frontal cortex. During NBS, muscle activity was monitored online by electromyography. The motor threshold, amplitudes and latencies for the abductor digiti minimi (ADM) and abductor pollicis brevis (APB) muscles were determined. To visualize the cortical areas represe…