Experimental Pain Picture System (EPPS): Development and Validation.

Pain-related pictures are useful for studying how individuals respond to pain-related stimulation. Such pictures can occasionally be found in databases for affective pictures. However, a validated database specifically for pain-related pictures is not available yet. In 2 experiments (N = 185 and 103, respectively), we developed and validated the Experimental Pain Pictures System (EPPS). In both experiments, negative valence, arousal, and painfulness ratings were compared between neutral-, sad-, and pain-related pictures. The pain-related pictures represented both deep and superficial somatic pain. Across the 2 experiments, pain-related pictures were judged as more negative, arousing, and painful than neutral pictures and more painful than sad pictures. The final EPPS contains 50 pictures of different painful events considered moderately to highly painful by participants. The EPPS is a valuable tool for studying pain-related responses, as it gives researchers a choice among many validated pictures depicting different types of pain, increasing the comparability between studies. PERSPECTIVE: This article presents the validation of the experimental pain pictures system, which consists of a set of pain-related pictures. The experimental pain pictures system is composed of pictures depicting different types of pain. Participants rated all the pictures as being negative, arousing, and painful.

No Evidence That Working Memory Modulates the Plasticity of the Nociceptive System, as Measured by Secondary Mechanical Hypersensitivity.

The effect of cognition on the plasticity of the nociceptive system remains controversial. In this study, we examined whether working memory can buffer against the development of secondary hypersensitivity. Thirty-five healthy women participated in 3 experimental conditions. In each condition, they underwent electrical stimulation of the skin for 2 minutes (middle-frequency electrical stimulation [MFS]), which induces secondary hypersensitivity. During MFS, participants executed either an individually tailored and rewarded n-back task (working memory condition), a rewarded reaction-time task (non-working memory condition), or no task at all (control condition). Before and after MFS, participants rated the self-reported intensity and unpleasantness of mechanical pinprick stimuli. Fear of MFS was also assessed. Heart rate variability was measured to examine potential differences between the 3 conditions and steady-state evoked potentials to the electrical stimulation were recorded to investigate differences in cortical responses. We report no significant difference in hypersensitivity between the 3 conditions. Moreover, engaging in the cognitive tasks did not affect the heart rate variability or the steady-state evoked potentials. Interestingly, higher fear of MFS predicted greater hypersensitivity. In conclusion, we found no evidence that working memory affects the plasticity of the nociceptive system, yet pain-related fear plays a role. PERSPECTIVE: This study shows that the execution of a cognitive task, irrespective of cognitive load or working memory, does not significantly modulate the development of secondary hypersensitivity, heart rate variability, or steady-state evoked potentials. However, higher pain-related fear seems to contribute to greater hypersensitivity.

The role of intolerance of uncertainty when solving the exploration-exploitation dilemma.

When making behavioral decisions, individuals need to balance between exploiting known options or exploring new ones. How individuals solve this exploration-exploitation dilemma (EED) is a key research question across psychology, leading to attempting to disentangle the cognitive mechanisms behind it. A potential predictive factor of performance in an EED is intolerance of uncertainty (IU), an individual difference factor referring to the extent to which uncertain situations are reported to be aversive. Here, we present the results of a series of exploratory analyses in which we tested the relationship between IU and performance in an EED task. For this, we compiled data from 3 experiments, in which participants received the opportunity to exploit different movements in order to avoid a painful stimulus and approach rewards. For decomposing performance in this task, we used different computational models previously employed in studies on the EED. Then, the parameters of the winning model were correlated with the scores of participants in the IU scale. Correlational and cluster analyses, within both frequentists and Bayesian frameworks, did not provide strong evidence for a relation between EED and IU, apart from the decay rate and the subscale "tendency to become paralyzed in the face of uncertainty". Given the theoretical relation between EED and IU, we propose research with different experimental paradigms.

Correction: The effect of cognitive effort on the sense of agency.

[This corrects the article DOI: 10.1371/journal.pone.0236809.].

The exploration-exploitation dilemma in pain: an experimental investigation.

ABSTRACT: Daily life consists of a chain of decisions. Typically, individuals may choose to pursue what they already know (exploitation) or to search for other options (exploration). This exploration-exploitation dilemma is a topic of interest across multiple scientific fields. Here we propose that investigating how individuals solve this dilemma may improve our understanding of how individuals make behavioral decisions (eg, avoidance) when facing pain. To this end, we present the data of 3 experiments in which healthy individuals were given the opportunity to choose between 4 different movements, with each movement being associated with different probabilities of receiving a painful outcome only (experiment 1) or pain and/or a reward (experiment 2). We also investigated whether participants stuck to their decisions when the contingencies between each movement and the painful/rewarding outcome changed during the task (experiment 3). The key findings across all experiments are the following: First, after initial exploration, participants most often exploited the safest option. Second, participants weighted rewards more heavily than receiving pain. Finally, after receiving a painful outcome, participants were more inclined to explore than to exploit a rewarding movement. We argue that by focusing more on how individuals in pain solve the exploration-exploitation dilemma is helpful in understanding behavioral decision making in pain.

The effect of cognitive effort on the sense of agency.

While we are performing a demanding cognitive task, not only do we have a sense of cognitive effort, we are also subjectively aware that we are initiating, executing and controlling our thoughts and actions (i.e., sense of agency). Previous studies have shown that cognitive effort can be both detrimental and facilitative for the experienced sense of agency. We hypothesized that the reason for these contradictory findings might lie in the use of differential time windows in which cognitive effort operates. The current study therefore examined the effect of cognitive effort exerted on the current trial, on the previous trial or across a block of trials on sense of agency, using implicit (Experiment 1) and explicit (Experiment 2) measures of sense of agency. We showed that the exertion of more cognitive control on current trials led to a higher explicit sense of agency. This surprising result was contrasted to previous studies to establish potential reasons for this surprising finding and to formulate recommendations for future studies.