Pain is a precious gift, arguably the most precious one that people get from their evolutionary history; yet, it is "a gift nobody wants". Without it, one can rarely survive their childhood; with it, one can hardly escape the fate of suffering from it sometime, somewhere. For those who do feel pain, the evolution has done something even more disappointing: pain perception varies widely among individuals. The same nociceptive stimulus may elicit unpredictably intense sensations in someone, yet be barely perceived by another. What drives such dramatic variability of pain perception?  

Previous studies have attempted to identify neural markers for the variability of pain sensitivity. However, such studies often fail to distinguish within-subject variability from between-subject variability, and for those which do treat the two sources of variability differently, the findings are not conclusive.

Recently, Dr. HU Li from the Institute of Psychology of the Chinese Academy of Sciences, together with Dr. Giandomenico Iannetti from University College London, has overcome methodological and analytical issues in existing studies, and demonstrated that brain oscillations in the gamma band [gamma-band event-related synchronization (γ-ERS)] reliably and selectively predict pain sensitivity across individuals.  

In three psychophysical and electrophysiological investigations, Dr. HU and Dr. Iannetti found that while many laser-evoked brain measures reflected subjective pain ratings at the within-subject level, only γ-ERS reliably distinguished subjective ratings within the same individual and coded pain sensitivity across different individuals in humans and rats alike.

Indeed, the temporal-spectral pattern of γ-ERS response reliably accurately predicted the intensity of pain between subjects. Importantly, γ-ERS did not track the between-subject reported intensity of nonpainful but equally salient auditory, visual, and non-nociceptive somatosensory stimuli.

Taken together, these results show that laser-induced gamma oscillations predict pain sensitivity across individuals reliably and selectively.  

This discovery of a neurophysiological trait reflecting cross-individual perceptual variability can shed insight into the mechanisms underlying perceptual and cognitive performance, and is of particular relevance in pain neuroscience where such variability is particularly high and poses significant challenges in clinical practice.  

The results, entitled "Neural indicators of perceptual variability of pain across species", was published online in PNAS on Jan. 14, 2019.

This work was funded by National Natural Science Foundation of China and the Informatization Special Project of Chinese Academy of Sciences.  

Fig. γ-ERS reflected both within- and between-subject variability of pain perception (Image by HU Li)