High-frequency oscillations of somatosensory evoked potentials and fields.

A short review of previous studies is presented on somatic, evoked high-frequency oscillations. Also described briefly is recent data on the detection of high-frequency oscillations to posterior tibial nerve stimulation, and also on both tangential (area 3b) and radial (area 1) dipoles to median nerve stimulation. The findings show that high-frequency oscillations are not specific to median nerve stimulation but represent ubiquitous activity in the primary somatosensory cortex. Modulation of high-frequency oscillations versus electric and magnetic N20, N20 (m), primary response by a wake-sleep cycle, by attention or interference, by aging, and in central nervous system diseases such as Parkinson's disease and myoclonus epilepsy are also presented. Finally, a gamma-aminobutyric acid inhibitory interneuron hypothesis is presented for high-frequency oscillations based primarily on the findings regarding reciprocal modulation of the high-frequency oscillations and the underlying magnetic N20 (N20m) by a wake-sleep cycle and by attention or interference.