Brain ImagingNeuronal responses to magnetic stimulation reveal cortical reactivity and connectivityIlmoniemi, Risto J.1,6; Virtanen, Juha1,2,3; Ruohonen, Jarmo1; Karhu, Jari1,4; Aronen, Hannu J.2; Näätänen, Risto3; Katila, Toivo1,5Author Information 1BioMag Laboratory, Medical Engineering Centre, Tukholmankatu 8 F, FIN-00290 Helsinki 2Department of Radiology, Helsinki University Central Hospital, Tukholmankatu 8 F, FIN-00290 Helsinki 3Cognitive Brain Research Unit, Department of Psychology, University of Helsinki, Helsinki 4Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio 5Laboratory of Biomedical Engineering, Helsinki University of Technology, Espoo, Finland 6Corresponding Author: Risto J. Ilmoniemi Received 24 July 1997; accepted 23 August 1997 NeuroReport: November 10th, 1997 - Volume 8 - Issue 16 - p 3537-3540 Buy 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. © Lippincott-Raven Publishers.