Effects of stimulus intensity increase on short-latency somatosensory evoked potentials: Application of polynomial curvature coefficients

Abstract

We assessed the influence of increasing stimulus intensity from motor threshold to pain threshold on short latency somatosensory evoked potentials recorded over the parietal and frontal scalp in 14 subjects during median nerve stimulation at the wrist. We used the curvature polynomial coefficient to evaluate alterations of the main components. The N20 and P27 curvature coefficients are not modified. The change of the N30 curvature coefficient is the result of shortened P45 latency. The increase of N60 curvature coefficient shows a great interindividual variability, probably due to a central amplification and synchronization or to involvement of nerve fibres with different excitability.

Abnormal cortical brain integration of somatosensory afferents in ALS

“…The reported alterations included a delayed peak latency with reduction of central and peripheral conduction velocity for 40 % and 20 % patients, respectively, and reduced amplitude for 20 % patients (Anziska and Cracco, 1983;Cosi et al, 1984;Dasheiff et al, 1985;Matheson et al, 1986;Subramaniam and Yiannikas, 1990;Zanette et al, 1990;Shefner et al, 1991;Gregory et al, 1993;Georgesco et al, 1994;Pugdahl et al, 2006;Hammad et al, 2007). In this present study, we did not find any difference in peak onset and latency between groups, reflecting a normal conduction velocity through large-diameter fibres and normal mean conduction velocity, respectively (Parain and Delapierre, 1991;Tanosaki et al, 1999;Shiga et al, 2001). However, we confirm evidence of consistently reduced SEPs, especially the late ones that have been understudied in ALS to date.…”

“…at lower stimulus intensities compared to N9. It has been proposed that this result was likely due to a differential recruitment of peripheral fibres and/or an occlusive phenomenon occurring at the central level, in the sub-cortical nuclei relaying the sensory inputs to the cerebral cortex (Lesser et al, 1979;Gandevia and Burke, 1984;Parain and Delapierre, 1991;Huttunen, 1995;Torquati et al, 2002;Lim et al, 2012).…”

Modulation of human corticospinal excitability by paired associative stimulation

“…Lakhani et al, 2012; Gatica Tossi et al, 2013), an effect that remains evident at 2.5 times MT (Urasaki et al, 1998). While components of the S1 SEP appear to saturate at some point below the pain threshold (PT) (Parain and Delapierre, 1991), MEG recordings suggest that the asymptote of the S2 response occurs at lower stimulation intensities than for the S1 response (Lin et al, 2003). In general the relationship between stimulus intensity and the overall magnitude of the SEP can be characterized as a decelerating power function (Hashimoto et al, 1992).…”

Neuromuscular electrical stimulation‐promoted plasticity of the human brain

“…1998). Components of the SEP recorded in S1 saturate at a level below the pain threshold (Parain & Delapierre, 1991), while the asymptote of the S2 response occurs at lower stimulation intensities than for the S1 response (Lin et al . 2003).…”