Neural Mechanisms of Attentional Switching Between Pain and a Visual Illusion Task: A Laser Evoked Potential Study

Andrej Stancak,Vicente Soto,Katerina Kokmotou,Nicholas Fallon,Stephanie Cook,Alessandra Fenu

doi:10.1007/s10548-017-0613-8

Abstract

Previous studies demonstrated that pain induced by a noxious stimulus during a distraction task is affected by both stimulus-driven and goal-directed processes which interact and change over time. The purpose of this exploratory study was to analyse associations of aspects of subjective pain experience and engagement with the distracting task with attention-sensitive components of noxious laser-evoked potentials (LEPs) on a single-trial basis. A laser heat stimulus was applied to the dorsum of the left hand while subjects either viewed the Rubin vase-face illusion (RVI), or focused on their pain and associated somatosensory sensations occurring on their stimulated hand. Pain-related sensations occurring with every laser stimulus were evaluated using a set of visual analogue scales. Factor analysis was used to identify the principal dimensions of pain experience. LEPs were correlated with subjective aspects of pain experience on a single-trial basis using a multiple linear regression model. A positive LEP component at the vertex electrodes in the interval 294–351 ms (P2) was smaller during focusing on RVI than during focusing on the stimulated hand. Single-trial amplitude variations of the P2 component correlated with changes in Factor 1, representing essential aspects of pain, and inversely with both Factor 2, accounting for anticipated pain, and the number of RVI figure reversals. A source dipole located in the posterior region of the cingulate cortex was the strongest contributor to the attention-related single-trial variations of the P2 component. Instantaneous amplitude variations of the P2 LEP component during switching attention towards pain in the presence of a distracting task are related to the strength of pain experience, engagement with the task, and the level of anticipated pain. Results provide neurophysiological underpinning for the use of distraction analgesia acute pain relief.

Highlights

Pain has been shown to be reduced while attention is directed to a stimulus occurring in a different sensory modality or consumed in an engaging cognitive task (Miron et al 1989)
Multiple cortical regions contributed to laser-evoked potentials (LEPs) during this latency interval, only one source dipole located in the posterior region of the cingulate cortex encoded effects of attentional distraction
Single-trial variations in subjective pain experience encompassing primarily the pain intensity and pricking sensation correlated with the instantaneous amplitudes of the P2 component during manipulation of attentional focus

Summary

Introduction

Pain has been shown to be reduced while attention is directed to a stimulus occurring in a different sensory modality or consumed in an engaging cognitive task (Miron et al 1989). Balancing pain experience with concurrent cognitive or sensory activities requires a switch mechanism which operates automatically on a scale of hundreds of milliseconds and takes into account instantaneous demands and motivational values of parallel tasks. The time interval following switching attention towards pain has been suggested to allow the background pain to invade the conscious mind and disrupt the cognitive performance further in chronic pain patients (Attridge et al 2016; Vlaeyen et al 2016). Pain intensity and performance in a distracting task have been shown to interact in a dose-dependent manner with the largest pain reduction and the largest disruption of performance occurring at the highest levels of both (Romero et al 2013)

Methods

Results

Conclusion