Age-associated changes in multimodal pain perception.

BACKGROUND: Pain sensitivity varies across multimodal somatosensory stimuli that can rely on different conductive fibres, which, when damaged, will lead to neuropathies. However, there is limited research examining the characteristics of perceived pain, particularly as affected by the ageing process, as induced by various somatosensory stimuli that may rely on small or large fibres. METHODS: Using heat and pressure stimuli on small and large fibres separately on both younger and older adults, this study examined age-associated changes in pain perception by measuring self-reported pain sensitivity, pain threshold and pain discriminability. RESULTS: Heat pain threshold was significantly positively correlated with age, but not pressure pain threshold. Pain threshold increased and pain discriminability decreased in response to heat stimuli in the older participants compared with the younger ones. CONCLUSION: An age-associated decline in heat pain perception was observed, suggesting an earlier degradation of heat perception. These findings provide new insight into understanding and assessing somatosensory disorders, which can help ageing populations better maintain healthy sensory functioning.

The dual facilitatory and inhibitory effects of social pain on physical pain perception.

Pain is a multi-dimensional phenomenon that encompasses both physical pain experienced physiologically and social pain experienced emotionally. The interactions between them are thought to lead to increased pain load. However, the effect of social pain on physical pain perception during interactions remains unclear. Four experiments were conducted merging physical and social pains to examine the behavioral pattern and neural mechanism of the effect of social pain on physical pain perception. Seemingly paradoxical effects of social pain were observed, which both facilitated and inhibited physical pain perception under different attention orientations. Brain imaging revealed that the posterior insula encoded the facilitatory effect, whereas the frontal pole engaged in the inhibitory effect. At a higher level, the thalamus further modulated both processes, playing a switch-like role under different concern statuses of social pain. These results provide direct evidence for the dual-pathway mechanism of the effect of social pain on physical pain.

Stigmatized experience is associated with exacerbated pain perception in depressed patients.

Patients with depression not only have to cope with depressive and physical symptoms but also face stigmatization due to mental illness. Pain is a clinical symptom of many patients with depression. However, it is unclear whether stigmatized experience associated with mental illness directly affects depressed patients' pain perception. Here, using the event reflection task, Study 1 (N = 95) examined whether stigmatized experiences due to depression would affect patients' self-reported pain assessment. Study 2 (N = 43) further employed thermal stimuli at different intensities to examine whether stigmatization would affect patients' evoked pain. We found that patients with depression who experienced stigmatization based on mental illness reported higher pain catastrophizing and performed increased pain perception for noxious stimuli than those who did not. Our studies provide first-hand experimental evidence of the effect of stigmatized experiences on depressed patients' pain perception. The findings contribute insights for improving clinical treatment, suggesting that interventions should minimize stigmatization associated with mental illness to help patients maintain healthier physical and psychological states.