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The role of executive functions in task-related analgesia
Rischer, Katharina Miriam; Gigl, Sandra; Dierolf, Angelika; González-Roldán, Ana Maria; Anton, Fernand; Van Der Meulen, Marian

Poster (2019, March)

Introduction: Recent research suggests that weaker executive functions may be linked to a higher risk of pain chronicity. However, little is known about how executive functions affect the modulation of acute pain. The present study aimed to investigate the impact of inhibitory control on the success of cognitive distraction from pain. Methods: Participants completed a battery of cognitive tasks (Go/NoGo, Color Stroop, Eriksen Flanker), assessing their cognitive inhibition and selective attention abilities. Additionally, self-report measures of pain catastrophizing and fear of pain were administered. In a pain distraction paradigm, participants completed either a cognitively demanding working memory task (2-back task) or a visually matched easy control task (target response task) while receiving warm or painful thermal stimuli to their left forearm. Nociceptive stimulus intensity was individually calibrated for each participant. Moreover, to maintain a similar level of task difficulty across participants, task speed was continuously adapted based on the participant's performance in the previous trials. Following each trial, participants rated the perceived intensity and unpleasantness of the thermal stimuli on visual analogue scales. Results: As expected, preliminary results indicate that the 2-back task, but not the target response task, successfully distracted participants from thermal pain, manifesting in significantly lower intensity and unpleasantness ratings. Importantly, the magnitude of the distraction effect was negatively associated with the Flanker effect. Discussion: In line with previous research, engaging in a cognitively demanding task led to significantly lower pain intensity and unpleasantness ratings when compared to an easy control task. Moreover, results indicate that better interference control abilities may predict greater task-related analgesia. Taken together, the results of the present study suggest that it is crucial to assess executive functions to develop a better understanding of the mechanisms behind cognitive distraction from pain.

Painful decisions: How classifying sensations can change the experience of pain
Van Der Meulen, Marian; Anton, Fernand; Petersen, Sibylle

in European Journal of Pain (2017)

Background: Categorizing perceptual stimuli is a mechanism for facilitating the processing of sensory input from our environment. This facilitation of perception is achieved through generalization (assimilation) of stimulus characteristics within categories and accentuation between categories. These categorization processes have been demonstrated in visual, auditory, tactile and social perception, but never in pain perception. Method: We presented participants with six thermal noxious stimuli, increasing in steps of 0.5 °C. In an experimental group, stimuli were assigned to two categories labelled A and B containing the three lower (A1, A2, A3) and three higher (B1, B2, B3) stimuli. A control group did not receive such category information (stimuli were labelled S1–S6). In a first part of the experiment, participants simply rated pain intensity and unpleasantness for all stimuli. In a second part, we presented stimuli without labels and participants had to identify the label of each stimulus. Results: We found evidence for categorization effects in both pain ratings and stimulus identification data. In particular, unpleasantness ratings within categories were more similar to each other, and ratings between categories less similar, in the experimental compared to control group. Participants in the experimental group also confused stimuli more often within than between categories, and were more confident about category membership of stimuli at the category border, compared to participants in the control group. Conclusions: Mere category information, using abstract category labels, significantly changes pain perception. Implications for our understanding of cognitive pain modulation mechanisms, as well as clinical implications of categorization effects are discussed. Significance: Categorization effects in pain perception are demonstrated. Classifying and labelling painful events can modulate early perceptual processes, lead to under- or overestimation of pain symptoms and affect decision-making behaviour related to pain.

The role of cognitive reappraisal in placebo analgesia: an fMRI study
Van Der Meulen, Marian; Kamping, Sandra; Anton, Fernand

in Social Cognitive and Affective Neuroscience (2017), (2017), 1-10

Placebo analgesia (PA) depends crucially on the prefrontal cortex (PFC), which is assumed to be responsible for initiating the analgesic response. Surprisingly little research has focused on the psychological mechanisms mediated by the PFC and underlying PA. One increasingly accepted theory is that cognitive reappraisal—the reinterpretation of the meaning of adverse events—plays an important role, but no study has yet addressed the possible functional relationship with PA. We studied the influence of individual differences in reappraisal ability on PA and its prefrontal mediation. Participants completed a cognitive reappraisal ability task, which compared negative affect evoked by pictures in a reappraise versus a control condition. In a subsequent fMRI session, PA was induced using thermal noxious stimuli and an inert skin cream. We found a region in the left dorsolateral PFC, which showed a positive correlation between placebo-induced activation and (i) the reduction in participants’ pain intensity ratings; and (ii) cognitive reappraisal ability scores. Moreover, this region showed increased placebo-induced functional connectivity with the periaqueductal grey, indicating its involvement in descending nociceptive control. These initial findings thus suggest that cognitive reappraisal mechanisms mediated by the dorsolateral PFC may play a role in initiating pain inhibition in PA