Inhibition of the neural activity by paired stimulation in somatosensory evoked potentials and high frequency oscillations

This study evaluated the inhibition of neural re-action induced by paired stimulation using somatosensory-evoked potentials (SEPs) and high frequency oscillations (HFOs) in healthy subjects. The paired stimulations were applied to the subject at the specific interval. We used three interstimulus intervals (ISIs: 60, 100 and 300 ms) to analyze SEPs components (P15, N20 and P25) and HFOs caused paired electrical stimuli which are delivered to right median nerve. SEPs has high-frequency component (about 600Hz) is called HFOs in the intrinsic latency near N20. Shorter ISIs (less than 100ms) decreased the P15-N20 and N20-P25 amplitude significantly. Furthermore, also the maximum amplitude and the intensity of HFOs (both early and late components) decreased significantly as the ISIs shorten. Hashimoto et al and Curio el al suggested early HFOs reflect population spikes in thalamo-cortical axons, and later may reflect in S1 within grey matter. Therefore, we hypothesis that population spike in the time series variation of neural population spikes decreased by paired stimulation to peripheral nerve. It may be non-invasive technique to investigate neural activity in human cortex.