Discrepancy between perceived pain and cortical processing: A voxel-based morphometry and contact heat evoked potential study

Abstract

This finding suggests that the discrepancy between pain ratings and the amplitude of evoked potentials is not solely related to measurement artifact, but rather attributable, in part, to anatomical differences between subjects.

Contact Heat Evoked Potentials Are Responsive to Peripheral Sensitization: Requisite Stimulation Parameters

“…As is evident in Figure 4, even a low number of stimulations (10) yield a larger and reliable vertex waveform, particularly at higher baseline temperatures. This is in line with previous CHEPs studies (Kramer et al, 2013(Kramer et al, , 2016, and was further demonstrated in our own comparison between N2 latencies calculated from 10 stimuli to 20 stimuli, respectively. However, compared to other forms of noxious stimulation (e.g., laser), evoked potentials arising from contact heat stimulation are less synchronized and subject to greater temporal dispersion and higher latency jitter (variability in latency among averaged trials) (Granovsky et al, 2008).…”

“…Irrespective of the baseline temperature, the target peak stimulation intensity was set to 52 • C. The different baseline temperature conditions are displayed in Figure 1. For each condition, 10 stimulations (Kramer et al, 2013(Kramer et al, , 2016 were applied with an 8-12 s inter-pulse interval (Jutzeler et al, 2016;Rosner et al, 2018). A low number of stimulations was used to avoid peripheral sensitization caused by repetitive cutaneous stimulation.…”

“…One possibility for N2 latency reductions in response to capsaicin is that type II AMH afferents are temporally recruited earlier in the periphery during contact heat stimulation. Conventionally, contact heat stimulation is delivered from a low (e.g., 35 • C) baseline to a peak temperature (e.g., 52 • C) at a fixed, nominal rate (e.g., 70 • C/s) (Kramer et al, 2012a(Kramer et al, ,b, 2013(Kramer et al, , 2016Haefeli et al, 2013Haefeli et al, , 2014b. This means that stimulation passes through lower temperatures before activating type II AMH nociceptors (at ≥∼42 • C) (Baumgartner et al, 2005).…”

Warm‐, hot‐ and pain‐related neural activities depending on baseline skin temperatures

“…Subjects were asked to relax and evaluate the intensity of the painful heat stimulation for five stimuli in each task with a visual analogue scale (VAS), in which 0 represented ‘not painful’ and 10 represented ‘an intensity that subjects were unable to tolerate’. In order to familiarize subjects and limit the startle effect, individuals were exposed to contact heat stimuli prior to the acquisition of evoked potentials, as described previously (Kramer et al., ). Under the Hot condition, the thermode baseline temperature was also set at 30, 35 and 40 °C tasks, respectively, and the heat pulse was delivered from each baseline temperature to 46 °C.…”

Temporal relationship between perceptual and physiological events triggered by nociceptive heat stimuli

“…Its main characteristic is the progressive increase in temperature, which, in the most conventional stimulation protocols 3 reaches the predetermined peak after some 300 ms. It is known that the time that receptors are exposed to a stimulus and the composition of the stimulus-induced afferent volley are important aspects for the processing of sensory inputs at the central nervous system 6,18,19 . In the study presented here, we have examined the effects of changes in the total time of exposure and energy of the stimulation on physiological, behavioral and cognitive responses.…”