Intense and sustained pain reduces cortical responses to auditory stimuli: implications for the interpretation of Heterotopic Noxious Conditioning Stimulation in humans

Abstract

Phasic pain stimuli are inhibited when they are applied concomitantly with a conditioning tonic stimulus at another body location (Heterotopic Noxious Conditioning Stimulation, HNCS). While this effect is thought to rely on a spino-bulbospinal mechanism in animals (Diffuse Noxious Inhibitory Controls, DNIC), the underlying neurophysiology in humans may further involve other pathways. In this study, we investigated the role of supraspinal mechanisms in HNCS by presenting auditory stimuli during a conditioning tonic painful stimulus (the Cold Pressor Test, CPT). Considering that auditory stimuli are not conveyed through the spinal cord, any changes in brain responses to auditory stimuli during HNCS can be ascribed entirely to supraspinal mechanisms. High-density electroencephalography (EEG) was recorded during HNCS and auditory stimuli were administered in three blocks, before, during, and after HNCS. Nociceptive Withdrawal Reflexes (NWRs) were recorded at the same time points to investigate spinal processing. Our results showed that AEPs were significantly reduced during HNCS. Moreover, the amplitude of the NWR was significantly diminished during HNCS in most participants. Given that spinal and supraspinal mechanisms operate concomitantly during HNCS, the possibility of isolating their individual contributions to DNIC-like effects in humans is questionable. We conclude that the net effects of HCNS cannot be measured independently from attentional/cognitive influences.

Combined Evaluation of Nociceptive Detection Thresholds and Evoked Potentials during Conditioned Pain Modulation: A Feasibility Study

“…This finding is also in line with earlier research, wherein lower EP amplitudes were reported during a CPM paradigm [5]. At present, it is debated whether this is a biomarker of DNIC efficiency, or just habituation to the stimulus [4,17]. Evaluation of the EEG data with analyses of more statistical power such as an LMM [18] could be helpful in evaluating the influence of the individual stimulus parameters to the signal.…”

Comparing Test-Retest Reliability of Entropy Methods: Complexity Analysis of Resting-State fMRI

“…This network shows activity increases upon detection of salient targets, especially when they appear in unexpected locations [48]. Of note, the most important factor in the visual network is sensing the physical metrics of the spatial layout [49], and the auditory network is primarily active when external stimuli are received [50]. In addition, the frontoparietal network can maintain control signals online in working memory from one or a small number of trials to the next, enabling it to implement task control on a faster trial-to-trial basis [51].…”

Sensorimotor effects of plasticity‐inducing percutaneous peripheral nerve stimulation protocols: a blinded, randomized clinical trial

“…Specifically, activation of TRPV1‐positive fibres (mainly nociceptors), induces hypoesthesia in humans (Magerl & Treede, 2004), meaning that the stimulation of one type of afferents could influence the processing of other, heterosynaptically connected, pathways. Moreover, synaptic plasticity is not the only potential mechanism, as our protocols are likely to activate other systems, such as descending modulation, autonomous nervous system or supraspinal mechanisms (Lin et al, 2020; Torta et al, 2019).…”