NEURONAL RESPONSES TO MAGNETIC STIMULATION REVEAL CORTICAL REACTIVITYAND CONNECTIVITY

MOTOR and visual cortices of normal volunteers were activated by trans cranial magnetic stimulation. The electrical brain activity resulting from the brief electromagnetic pulse was recorded with high-resolution electroencephalography (HR-EEG) and located using inversion algorithm s. The stimulation of the left sensorimotor hand area elicited an imme diate response at the stimulated site. The activation had spread to ad jacent ipsilateral motor areas within 5-10 ms and to homologous region s in the opposite hemisphere within 20 ms. Similar activation patterns were generated by magnetic stimulation of the visual cortex. This new non-invasive method provides direct information about cortical reacti vity and area-to-area neuronal connections.