Neuronal responses to magnetic stimulation reveal cortical reactivity and connectivity

TLDR

Transcranial magnetic stimulation of motor and visual cortices in healthy volunteers was recorded with high‑resolution EEG and source‑localized via inversion algorithms. Stimulation of the left sensorimotor hand area produced an immediate local response that propagated to adjacent ipsilateral motor regions within 5–10 ms and to homologous contralateral areas within 20 ms, with analogous patterns observed in the visual cortex, demonstrating that this non‑invasive technique yields direct insight into cortical reactivity and inter‑areal connectivity.

Abstract

MOTOR and visual cortices of normal volunteers were activated by transcranial magnetic stimulation. The electrical brain activity resulting from the brief electromagnetic pulse was recorded with high-resolution electroencephalography (HR-EEG) and located using inversion algorithms. The stimulation of the left sensorimotor hand area elicited an immediate response at the stimulated site. The activation had spread to adjacent ipsilateral motor areas within 5–10 ms and to homologous regions 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 reactivity and area-to-area neuronal connections.