Analgesia induced by self-initiated electrotactile sensation is mediated by top-down modulations

Sexism-Related Stigma Affects Pain Perception

People with stigmatized characteristics tend to be devalued by others in a given society. The negative experiences related to stigma cause individuals to struggle as they would if they were in physical pain and bring various negative outcomes in the way that physical pain does. However, it is unclear whether stigma related to one's identity would affect their perception of physical pain. To address this issue, using sexism-related paradigms, we found that females had reduced pain threshold/tolerance in the Cold Pressor Test (Experiment 1) and an increased rating for nociceptive laser stimuli with fixed intensity (Experiment 2). Additionally, we observed that there was a larger laser-evoked N1, an early laser-evoked P2, and a larger magnitude of low-frequency component in laser-evoked potentials (LEPs) in the stigma condition than in the control condition (Experiment 3). Our study provides behavioral and electrophysiological evidence that sexism-related stigma affects the pain perception of females.

Brain regions preferentially responding to transient and iso-intense painful or tactile stimuli

How pain emerges from cortical activities remains an unresolved question in pain neuroscience. A first step toward addressing this question consists in identifying brain activities that occur preferentially in response to painful stimuli in comparison to non-painful stimuli. A key confound that has affected this important comparison in many previous studies is the intensity of the stimuli generating painful and non-painful sensations. Here, we compared the brain activity during iso-intense painful and tactile sensations sampled by functional MRI in 51 healthy participants. Specifically, the perceived intensity was recorded for every stimulus and only the stimuli with rigorously matched perceived intensity were selected and compared between painful and tactile conditions. We found that all brain areas activated by painful stimuli were also activated by tactile stimuli, and vice versa. Neural responses in these areas were correlated with the perceived stimulus intensity, regardless of stimulus modality. More importantly, among these activated areas, we further identified a number of brain regions showing stronger responses to painful stimuli than to tactile stimuli when perceived intensity was carefully matched, including the bilateral opercular cortex, the left supplementary motor area and the right frontal middle and inferior areas. Among these areas, the right frontal middle area still responded more strongly to painful stimuli even when painful stimuli were perceived less intense than tactile stimuli, whereas in this condition other regions showed stronger responses to tactile stimuli. In contrast, the left postcentral gyrus, the visual cortex, the right parietal inferior gyrus, the left parietal superior gyrus and the right cerebellum had stronger responses to tactile stimuli than to painful stimuli when perceived intensity was matched. When tactile stimuli were perceived less intense than painful stimuli, the left postcentral gyrus and the right parietal inferior gyrus still responded more strongly to tactile stimuli while other regions now showed similar responses to painful and tactile stimuli. These results suggest that different brain areas may be engaged differentially when processing painful and tactile information, although their neural activities are not exclusively dedicated to encoding information of only one modality but are strongly determined by perceived stimulus intensity regardless of stimulus modality.

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Transient painful and tactile stimuli activate the same brain areas.

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Neural activity in these areas encode stimulus intensity.

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Among these areas, a few may be engaged differentially in pain and touch processing.

Reminders of Mortality Alter Pain-Evoked Potentials in a Chinese Sample

Pain is of evolutionary importance to human survival. However, the perception of pain could be changed when death-related thoughts are accessible. Although the influence of mortality salience (MS) on pain processing has been investigated in Westerners recently, it is unclear whether this effect is constrained by specific culture context since humans may employ cultural worldviews to defend the existence problem. The current study tested whether and how MS affected pain processing in a Chinese male sample. We primed participants with sentences indicating MS or negative affect (NA) on either of two days. Both before and after the priming, event-related potentials (ERPs) elicited by painful and non-painful electrical stimulations were recorded. Results showed that pain-evoked potentials were identified as an early negative complex N60-P90-N130 and a late positivity P260. Pain-evoked N130 after MS priming was larger than that after NA priming. Meanwhile, pain-evoked P260 decreased after MS priming but not after NA priming. These findings indicate that reminders of mortality affect both early sensory and late cognitive neural responses related to physical pain. Although previous studies reporting an increased effect of MS on perceived pain intensity in Westerners, we found an unchanged or possibly reduced effect in Chinese. Thus, the current work provides insight into a culture-sensitive perspective on how pain processing would be modulated when existential problem occurs.

Comparing intensities and modalities within the sensory attenuation paradigm: Preliminary evidence

It is well-documented that the intensity of a self-generated somatosensory stimulus is perceived to be attenuated in respect to an identical stimulus generated by others. At present, it is not clear whether such a phenomenon, known as somatosensory attenuation, is based not only on feedforward motor signals but also on re-afferences towards the body. To answer this question, in the present pilot investigation on twelve healthy subjects, three types of stimulations (sensory non-nociceptive electrical – ES, nociceptive electrical – NES, and vibrotactile – VTS) and intensities (1 = sensory threshold ∗ 2.5 + 2 mA, 2 = sensory threshold ∗ 2.5 + 3 mA, 3 = sensory threshold ∗ 2.5 + 4 mA for ES and NES; 1 = sensory threshold ∗ 2 Hz, 2 = sensory threshold ∗ 3 Hz, 3 = sensory threshold ∗ 4 Hz for VTS) have been directly compared in a somatosensory attenuation paradigm. The results show that the attenuation effect emerged only with electrical stimuli and that it increased with higher intensities. These pilot findings suggest that, depending on the type and the intensity of stimulation, re-afferences can have a role in somatosensory attenuation. Additionally, it is possible to speculate the effect is present only with electrical stimuli because those stimuli are prospectively judged as potentially dangerous. This, in turn, would optimize planning successful reactions to incoming threatening stimuli.