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

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.

Pain and Distraction According to Sensory Modalities: Current Findings and Future Directions

“…Different results were found by Stancak et al., who compared 2 counterbalanced conditions in 24 adults with acute pain: distraction and focusing on the pain. In the distraction condition, the participants were asked to count the figures contained in the Rubin vase optical illusion, while pain was induced by laser pulses on one hand.…”

“…However, 2 studies in adults presented a sample of 3 and 8 subjects, and a third study did not present positive results in pain reduction. Nevertheless, in this last study, the tendency was for the distraction group to exhibit less pain than the control group; therefore, with a larger sample size it could have reached statistical significance. As a result, the level of evidence is low, and the results have a high risk of bias and provide insufficient evidence to evaluate the effect of distraction tasks in pain‐free adults who use the sense of sight.…”

Effects of Caffeine on Event-Related Potentials and Neuropsychological Indices After Sleep Deprivation

“…P2 is believed to reflect the post-synaptic activity of a specific neural process, and it represents aspects of higher-order perceptual processing, modulated by attention, linguistic contextual information, memory, and repetition effects (Liu et al, 2014 ). The exact function and neural source of the P2 component are not yet known, but some evidence has indicated that P2 may reflect general neural processes that occur when a visual (or other sensory) input is compared with an internal representation or expectation in the memory or language cortex (Stancak et al, 2018 ). Therefore, the larger amplitude of the P2 ERP component in Go trials may reflect the improved pre-attention brain function produced by caffeine administration after TSD.…”