Facilitation dynamics of late somatosensory evoked potentials after sural nerve stimulation

Publication date: Available online 16 April 2016
Source:Clinical Neurophysiology
Author(s): I. Zakharova, J.C. Kohlmeyer, M.E. Kornhuber
ObjectiveSomatosensory evoked potentials (SSEP) could be suitable for elucidating the properties of synaptic potentials (SP). Two experiments were designed for this purpose.Methods1^st experiment: the sural nerve was stimulated in 13 subjects with single or trains of 3 stimuli (1Hz or 0.4Hz), the within train interstimulus interval (ISI) was stepwise extended from 2 to 10ms. Cz' against Fz, time interval 500ms. 2^nd experiment: Gating was investigated in a paired stimulus paradigm with intervals of 0.7, 1, 2, 5 s in 15 subjects after single and train stimuli (ISI 3ms) with equal stimulus and recording positions.Results1^stexperiment: N1-P1, P1-N2a and P2-N2b but not N37-P40 displayed a significant gain in amplitude following train stimuli compared with single stimuli. Significantly larger N1-P1 amplitude values were observed with 0.4Hz stimulus repetition compared with 1.0Hz. Short ISIs of 2-4ms led to higher N1-P1 amplitudes than obtained with longer ISIs of 7-10ms. 2^ndexperiment: recovery of the habituated N1-P1 amplitude was complete when the 2^nd of 2 stimuli followed after 2s.ConclusionsSSEP vertex potential amplitudes (especially N1-P1) recorded after train stimuli presumably reflect the decay dynamics of excitatory postsynaptic potentials. Recovery of the habituated N1 (2^nd experiment) was complete within 2s.SignificanceOur study may be relevant to study properties of excitatory synaptic potentials in diseases of the central nervous system such as e.g. epilepsy or migraine.



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