Somatosensory evoked potentials elicited by mechanical and electrical stimulation of each single pain or tactile spot of the skin.

Abstract

Single pain and tactile spots on the dorsum of the right hand in man were stimulated by electric pulses and mechanical taps using a needle to . a pain spot and a horse tail bristle to a tactile one. Somatosensory evoked potentials (SEPs) and far field potentials (FFPs) were observed in three volunteers by averaging of 200 or 400 samples of responses recorded from scalp points corresponding to the left and right somatosensory areas (LSA and RSA). For SEP measurements, the difference between responses at LSA and RSA was obtained in order to specify the optimum response at LSA. The patterns of SEPs elicited by mechanical or electrical stimulation to a pain spot were similar to those to a tactile one. The typical SEP to mechanical stimulation consisted of N23, P31, N40, P49, N64, P87, N114 and P147, while thit to electrical stimulation did of N24, P33, N42, P52, N66, P95, N122 and P156. Consequently, mean peak latencies of the later components in SEPs elicited by mechanical stimulation were earlier than those to electrical one. The SEP amplitudes for mechanical stimulation were 1-3 µV and were larger than those to electrical one. By mechanical stimulation FFPs could not be obtained, while by electrical stimulation FFPs in peak latency of approximately 14 msec (P14) were seen. No specific components to sensory modality of pain or tactile sensation were observed either in SEPs or in FFPs.somatosensory evoked potential (SEP); sensory spot; mechanical skin stimulation Several authors (Halliday and Wakefield 1963;Giblin 1964;Bergamini et al. 1966;Larson et al. 1966) have suggested that the early components and some of the late ones of somatosensory evoked potentials (SEPs) elicited by electrical stimulation of mixed peripheral nerves are induced mainly by impulses ascending via the dorsal column-medial lemniscus pathway.On the other hand, Nakanishi et al. (1974) have postulated that the afferent impulses responsible for SEPs to mechanical stimulation travel through the ventrolateral spinothalamic tracts. If so, a question rises whether there are some

Cortical activity evoked by an acute painful tissue-damaging stimulus in healthy adult volunteers

“…However, it may also represent a difference in the saliency between an innocuous control and a noxious stimulation (Iannetti and Mouraux 2010; Legrain et al 2011). The vertex potential following mechanical stimulation found in the present study and reported by others (Bromm and Scharein 1982; Iannetti et al 2007; Yamauchi et al 1981) has a shorter latency (80–280 ms) than that following laser stimulation (200–380 ms; Cruccu et al 2008; Treede et al 2003) but is nevertheless consistent with Aδ activation. Contact heat- and laser-evoked potentials are mediated by thermonociceptive cutaneous fibers, and it is not surprising that the mechanonociceptive evoked responses reported have a shorter latency.…”

“…The N peak evoked by the lance and the sham control is comparable to that evoked by mechanical pinprick stimulation (Bromm and Scharein 1982; Iannetti et al 2007; Yamauchi et al 1981). As with our findings, this peak did not distinguish innocuous from noxious stimulation and is therefore likely to arise from Aβ tactile afferent input.…”

Comparison of cortical potentials evoked by mechanical and electrical stimulation of the rectum

“…Therefore, while receptor activation could account for some of the latency difference in our study, the delay for balloon inflation probably accounts for most of the latency difference. The CEP amplitude following electrical and mechanical CEPs has varied between studies, with mechanically evoked CEPs being reported as having a smaller, 29 similar, 14 or larger 30 amplitude than electrically evoked CEPs. However, as no attempt was made in these studies to control for the intensity of electrical and mechanical stimulation, it is difficult to interpret the reported amplitude differences.…”