Neurocognitive evidence for mental imagery-driven hypoalgesic and hyperalgesic pain regulation.

Mental imagery has the potential to influence perception by directly altering sensory, cognitive, and affective brain activity associated with imagined content. While it is well established that mental imagery can both exacerbate and alleviate acute and chronic pain, it is currently unknown how imagery mechanisms regulate pain perception. For example, studies to date have been unable to determine whether imagery effects depend upon a general redirection of attention away from pain or focused attentional mechanisms. To address these issues, we recorded subjective, behavioral and ERP responses using 64-channel EEG while healthy human participants applied a mental imagery strategy to decrease or increase pain sensations. When imagining a glove covering the forearm, participants reported decreased perceived intensity and unpleasantness, classified fewer high-intensity stimuli as painful, and showed a more conservative response bias. In contrast, when imagining a lesion on the forearm, participants reported increased pain intensity and unpleasantness, classified more low-intensity stimuli as painful, and displayed a more liberal response bias. Using a mass-univariate approach, we further showed differential modulation of the N2 potentials across conditions, with inhibition and facilitation respectively increasing and decreasing N2 amplitudes between 122 and 180 ms. Within this time window, source localization associated inhibiting vs. facilitating pain with neural activity in cortical regions involved in cognitive inhibitory control and in the retrieval of semantic information (i.e., right inferior frontal and temporal regions). In contrast, the main sources of neural activity associated with facilitating vs. inhibiting pain were identified in cortical regions typically implicated in salience processing and emotion regulation (i.e., left insular, inferior-middle frontal, supplementary motor and precentral regions). Overall, these findings suggest that the content of a mental image directly alters pain-related decision and evaluative processing to flexibly produce hypoalgesic and hyperalgesic outcomes.

Synchronized arousal between performers and related spectators in a fire-walking ritual.

Collective rituals are present in all known societies, but their function is a matter of long-standing debates. Field observations suggest that they may enhance social cohesion and that their effects are not limited to those actively performing but affect the audience as well. Here we show physiological effects of synchronized arousal in a Spanish fire-walking ritual, between active participants and related spectators, but not participants and other members of the audience. We assessed arousal by heart rate dynamics and applied nonlinear mathematical analysis to heart rate data obtained from 38 participants. We compared synchronized arousal between fire-walkers and spectators. For this comparison, we used recurrence quantification analysis on individual data and cross-recurrence quantification analysis on pairs of participants' data. These methods identified fine-grained commonalities of arousal during the 30-min ritual between fire-walkers and related spectators but not unrelated spectators. This indicates that the mediating mechanism may be informational, because participants and related observers had very different bodily behavior. This study demonstrates that a collective ritual may evoke synchronized arousal over time between active participants and bystanders. It links field observations to a physiological basis and offers a unique approach for the quantification of social effects on human physiology during real-world interactions.

Expectations contribute to reduced pain levels during prayer in highly religious participants.

Although the use of prayer as a religious coping strategy is widespread and often claimed to have positive effects on physical disorders including pain, it has never been tested in a controlled experimental setting whether prayer has a pain relieving effect. Religious beliefs and practices are complex phenomena and the use of prayer may be mediated by general psychological factors known to be related to the pain experience, such as expectations, desire for pain relief, and anxiety. Twenty religious and twenty non-religious healthy volunteers were exposed to painful electrical stimulation during internal prayer to God, a secular contrast condition, and a pain-only control condition. Subjects rated expected pain intensity levels, desire for pain relief, and anxiety before each trial and pain intensity and pain unpleasantness immediately after on mechanical visual analogue scales. Autonomic and cardiovascular measures provided continuous non-invasive objective means for assessing the potential analgesic effects of prayer. Prayer reduced pain intensity by 34 % and pain unpleasantness by 38 % for religious participants, but not for non-religious participants. For religious participants, expectancy and desire predicted 56-64 % of the variance in pain intensity scores, but for non-religious participants, only expectancy was significantly predictive of pain intensity (65-73 %). Conversely, prayer-induced reduction in pain intensity and pain unpleasantness were not followed by autonomic and cardiovascular changes.

Perceptual inference and autistic traits.

Autistic people are better at perceiving details. Major theories explain this in terms of bottom-up sensory mechanisms or in terms of top-down cognitive biases. Recently, it has become possible to link these theories within a common framework. This framework assumes that perception is implicit neural inference, combining sensory evidence with prior perceptual knowledge. Within this framework, perceptual differences may occur because of enhanced precision in how sensory evidence is represented or because sensory evidence is weighted much higher than prior perceptual knowledge. In this preliminary study, we compared these models using groups with high and low autistic trait scores (Autism-Spectrum Quotient). We found evidence supporting the cognitive bias model and no evidence for the enhanced sensory precision model.

Music training and empathy positively impact adults' sensitivity to infant distress.

Crying is the most powerful auditory signal of infant need. Adults' ability to perceive and respond to crying is important for infant survival and in the provision of care. This study investigated a number of listener variables that might impact on adults' perception of infant cry distress, namely parental status, musical training, and empathy. Sensitivity to infant distress was tested using a previously validated task, which experimentally manipulated distress by varying the pitch of infant cries. This task required that participants discriminate between pitch differences and interpret these as differences in infant distress. Parents with musical training showed a significant advantage on this task when compared with parents without. The extent of the advantage was correlated with the amount of self-reported musical training. For non-parents, individual differences in empathy were associated with task performance, with higher empathy scores corresponding to greater sensitivity to infant distress. We suggest that sensitivity to infant distress can be impacted by a number of listener variables, and may be amenable to training.

Using complexity metrics with R-R intervals and BPM heart rate measures.

Lately, growing attention in the health sciences has been paid to the dynamics of heart rate as indicator of impending failures and for prognoses. Likewise, in social and cognitive sciences, heart rate is increasingly employed as a measure of arousal, emotional engagement and as a marker of interpersonal coordination. However, there is no consensus about which measurements and analytical tools are most appropriate in mapping the temporal dynamics of heart rate and quite different metrics are reported in the literature. As complexity metrics of heart rate variability depend critically on variability of the data, different choices regarding the kind of measures can have a substantial impact on the results. In this article we compare linear and non-linear statistics on two prominent types of heart beat data, beat-to-beat intervals (R-R interval) and beats-per-min (BPM). As a proof-of-concept, we employ a simple rest-exercise-rest task and show that non-linear statistics-fractal (DFA) and recurrence (RQA) analyses-reveal information about heart beat activity above and beyond the simple level of heart rate. Non-linear statistics unveil sustained post-exercise effects on heart rate dynamics, but their power to do so critically depends on the type data that is employed: While R-R intervals are very susceptible to non-linear analyses, the success of non-linear methods for BPM data critically depends on their construction. Generally, "oversampled" BPM time-series can be recommended as they retain most of the information about non-linear aspects of heart beat dynamics.