Facilitation of Late Somatosensory Evoked Potentials by Electrical Train Stimuli.

Abstract Somatosensory evoked potentials (SSEP) may reflect synaptic events and could be suitable to characterise the short-time plasticity of synaptic potentials (SP). For this purpose, the left superficial radial nerve was stimulated in 7 subjects with single or trains of 3 stimuli (C4′ against Fz, time interval 500 ms, 1 Hz or 0.4 Hz). The within train interstimulus intervals (ISI) were varied from 2 ms to 10 ms. N20, N1 and N2 displayed a significant gain in amplitude following train stimuli compared with single stimuli. Short ISIs of 2–4 ms led to higher amplitudes of N20, N1 and N2 compared with longer ISIs of 7–10 ms. In general, larger amplitude values were observed with 0.4 Hz stimulus repetition compared with 1.0 Hz. This data reflects synaptic facilitation and refractoriness/habituation. Our results could be helpful to non-invasevely investigate synaptic decay dynamics by late SSEP in diseases of the central nervous system such as migraine or epilepsy.