Facilitation dynamics of late somatosensory evoked potentials after sural nerve stimulation.
Somatosensory evoked potentials (SSEPs) could be suitable for elucidating the properties of synaptic potentials (SPs). Two experiments were designed for this purpose.



1st 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. 2nd experiment: Gating was investigated in a paired stimulus paradigm with intervals of 0.7, 1, 2, 5s in 15 subjects after single and train stimuli (ISI 3ms) with equal stimulus and recording positions.



1st experiment: 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. 2nd experiment: recovery of the habituated N1-P1 amplitude was complete when the 2nd of 2 stimuli followed after 2s.



SSEP vertex potential amplitudes (especially N1-P1) recorded after train stimuli presumably reflect the decay dynamics of excitatory postsynaptic potentials. Recovery of the habituated N1 (2nd experiment) was complete within 2s.



Our 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.
Dept. of Neurology, Universitätsklinikum Halle (Saale), Ernst-Grube-Str. 40, 06120 Halle (Saale), Germany.
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Zakharova
Dept. of Neurology, Universitätsklinikum Halle (Saale), Ernst-Grube-Str. 40, 06120 Halle (Saale), Germany.
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Kohlmeyer
Dept. of Neurology, Universitätsklinikum Halle (Saale), Ernst-Grube-Str. 40, 06120 Halle (Saale), Germany. Electronic address: malte.kornhuber@medizin.uni-halle.de.
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Kornhuber
D000328:Adult; D005073:Evoked Potentials, Somatosensory; D019706:Excitatory Postsynaptic Potentials; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013497:Sural Nerve / Q000502:physiology*; D004561:Transcutaneous Electric Nerve Stimulation
Augmentation; Electrical train stimuli; Habituation; Late somatosensory evoked potentials N1, N2a, N2b; Refractoriness; Synaptic plasticity