Application of Navigated Transcranial Magnetic Stimulation to Map the Supplementary Motor Area in Healthy Subjects.

PURPOSE: The supplementary motor area is involved in the planning and coordination of movement sequences. This study investigates the potential of repetitive navigated transcranial magnetic stimulation for systematic mapping of the supplementary motor area by interfering with normal movement coordination processing.

METHODS: Ten healthy females (median age: 23.5 years) performed the Jebsen-Taylor Hand Function Test, first without stimulation (baseline) and afterward during application of repetitive navigated transcranial magnetic stimulation with 10 Hz to 6 cortical sites located within the supplementary motor area of both hemispheres. The test completion times (TCTs) were then compared between baseline performances and performances during stimulation.

RESULTS: We found significant slowing of TCTs in simulated page turning (baseline TCT 3.68 ± 0.67 seconds vs. stimulation TCT 4.04 ± 0.63 seconds, P = 0.0136), lifting small objects (baseline TCT 5.11 ± 0.72 seconds vs. stimulation TCT 5.47 ± 0.66 seconds, P = 0.0010), and simulated feeding (baseline TCT 6.10 ± 0.73 seconds vs. stimulation TCT 6.59 ± 0.81 seconds, P = 0.0027). Three other subtests were not affected, whereas one subtest was performed significantly faster (baseline TCT 17.09 ± 7.31 seconds vs. stimulation TCT 15.44 ± 5.72 seconds, P = 0.0073) under stimulation.

CONCLUSIONS: Repetitive navigated transcranial magnetic stimulation is capable of influencing the performance of healthy participants in a task relying on hand coordination. Our approach can serve as a mapping tool for the supplementary motor area, potentially relevant for preoperative diagnostics in patients with brain tumors, epilepsy, or other brain lesions to improve outcome and potentially predict clinical course and postoperative recovery.