Effects on EEG of Low (1Hz) and High (15Hz) Frequency Repetitive Transcranial Magnetic Stimulation of the Visual Cortex: A Study in the Anesthetized Cat

Here we confirm our earlier findings that showed 1Hz rTMS over the primary visual cortex of the anesthetized cat, known to cause inhibition of the cortex, induces an increase in power in the slow, delta band of the EEG. We also demonstrate that these inhibitory effects of 1Hz rTMS may be measured as changes of spatiotemporal receptive field pa- rameters at the single cell level. We extend these observations to show that higher frequency stimulation of the cortex at 15Hz has the opposite effect of decreasing delta activity, which was also accompanied by significant increases in theta, alpha and beta bands. This highly reproducible EEG change may be useful as a simple marker to predict inhibitory or ex- citatory rTMS effects known to be dependent upon stimulation frequency.