Pain: Behavioural expression and response in an evolutionary framework

Reconfiguring Pain Interpretation Within a Social Model of Health Using a Simplified Version of Wilber's All Quadrant All Levels Framework: An Integral Vision

Despite the proliferation of biomedical and psychological treatments, the global burden of chronic intractable (long-term) pain remains high-a treatment-prevalence paradox. The biopsychosocial model, introduced in the 1970s, is central to strategies for managing pain, but has been criticised for being decontextualised and fragmented, compromising the effectiveness of healthcare pain support services and patient care. The aim of this study was to apply a simplified version of Ken Wilber's All Quadrant All Levels (AQAL) framework to pain in a healthcare context to advance a biopsychosocial understanding. Utilising domain knowledge, the author mapped features of pain and coping to intrasubjective, intraobjective, intersubjective, and interobjective quadrants (perspectives), as well as levels of psychological development. Narratives were crafted to synthesize the findings of mapping with literature from diverse disciplines within the contexts of salutogenesis and a social model of health. The findings showed that AQAL-mapping enhanced contextual biopsychosocial coherence and exposed the conceptual error of reifying pain. Its utility lay in highlighting upstream influences of the painogenic environment, supporting the reconfiguration of pain within a social model of health, as exemplified by the UK's Rethinking Pain Service. In conclusion, a simple version of the AQAL framework served as a heuristic device to develop an integral vision of pain, opening opportunities for health promotion solutions within a salutogenic context.

The Intersection of Interoception and Anticipation Related to Pain

This chapter focuses on the interconnectedness of bodily awareness, emotion, and time perception, focusing on the roles of interoception and anticipation, pioneered by A.D. (Bud) Craig and advanced by contemporary research. Pain, a pivotal aspect of human experience, serves as a conduit for understanding our relationship with the world. Anticipation of pain, vital for survival, influences subjective pain experiences and is modulated by factors such as physiological reactivity and contextual cues. Emotional states significantly shape pain perception, with chronic pain conditions and affective disorders characterized by dysregulated pain modulation mechanisms. We discuss a state space model for pain, wherein pain functions as a latent construct shaped by both anticipatory and contemporaneous factors. Understanding these mechanisms is critical for informing clinical interventions aimed at pain management and highlights the intersection of interoception, emotion, and pain.

Neuroimmune Pain and Its Manipulation by Pathogens

Recent studies highlight extensive crosstalk that exists between sensory neurons responsible for pain and the immune system. Cutaneous pain neurons detect harmful microbes, recruit immune cells, and produce anticipatory immunity in nearby tissues. These complementary systems generally protect hosts from infections. At the same time, neuroimmune pain is vulnerable to manipulation. Some pathogens evade immunity activated by nociceptors by producing opioid analogs and by interfering with sensory nerve function. Other organisms manipulate neuroimmune pain by increasing it. Hosts may gain protection from interference by adjusting pain sensitivity. Nociceptive sensitization follows expectations of signal detection theory and the smoke detector principle, allowing pain to be more easily triggered in response to microbial threats and damage. However, pain sensitization at the spinal level and cortical responses to pain are themselves the target of manipulation by parasites and other organisms. Here we review examples of parasites, bacteria, and other medically important organisms that interfere with pain signaling and describe their implications for public health, infectious disease, and the treatment of pain.

Unveiling the Truth in Pain: Neural and Behavioral Distinctions Between Genuine and Deceptive Pain

Background/Objectives: Fake pain expressions are more intense, prolonged, and include non-pain-related actions compared to genuine ones. Despite these differences, individuals struggle to detect deception in direct tasks (i.e., when asked to detect liars). Regarding neural correlates, while pain observation has been extensively studied, little is known about the neural distinctions between processing genuine, fake, and suppressed pain facial expressions. This study seeks to address this gap using authentic pain stimuli and an implicit emotional processing task. Methods: Twenty-four healthy women underwent an fMRI study, during which they were instructed to complete an implicit gender discrimination task. Stimuli were video clips showing genuine, fake, suppressed pain, and neutral facial expressions. After the scanning session, participants reviewed the stimuli and rated them indirectly according to the intensity of the facial expression (IE) and the intensity of the pain (IP). Results: Mean scores of IE and IP were significantly different for each category. A greater BOLD response for the observation of genuine pain compared to fake pain was observed in the pregenual anterior cingulate cortex (pACC). A parametric analysis showed a correlation between brain activity in the mid-cingulate cortex (aMCC) and the IP ratings. Conclusions: Higher IP ratings for genuine pain expressions and higher IE ratings for fake ones suggest that participants were indirectly able to recognize authenticity in facial expressions. At the neural level, pACC and aMCC appear to be involved in unveiling the genuine vs. fake pain and in coding the intensity of the perceived pain, respectively.

The Locus Coeruleus in Chronic Pain

Pain perception is the consequence of a complex interplay between activation and inhibition. Noradrenergic pain modulation inhibits nociceptive transmission and pain perception. The main source of norepinephrine (NE) in the central nervous system is the Locus Coeruleus (LC), a small but complex cluster of cells in the pons. The aim of this study is to review the literature on the LC-NE inhibitory system, its influence on chronic pain pathways and its frequent comorbidities. The literature research showed that pain perception is the consequence of nociceptive and environmental processing and is modulated by the LC-NE system. If perpetuated in time, nociceptive inputs can generate neuroplastic changes in the central nervous system that reduce the inhibitory effects of the LC-NE complex and facilitate the development of chronic pain and frequent comorbidities, such as anxiety, depression or sleeping disturbances. The exact mechanisms involved in the LC functional shift remain unknown, but there is some evidence that they occur through plastic changes in the medial and lateral pathways and their brain projections. Additionally, there are other influencing factors, like developmental issues, neuroinflammatory glial changes, NE receptor affinity and changes in LC neuronal firing rates.