When seeing a doctor, do you feel your pain is being accurately assessed? The doctor may ask you to verbally report how painful you are or to fill out a questionnaire. Traditionally, these are the only ways available to assess pain, since other people cannot directly share your pain experience. However, these methods can often be unreliable and biased. Many studies thus attempt to objectively assess pain using neural responses. Recently, a new study led by Dr. HU Li from Institute of Psychology, Chinese Academy of Sciences, has shown that pain-related gamma-band oscillations (GBOs) can objectively reflect individuals’ pain perception, but there are different “kinds” of GBOs under different circumstances.
GBOs, the brain waves within the frequency range from 30 to 100 Hz, are one of the most selective biomarkers of pain perception. Previous studies by Dr. HU's research team have already demonstrated that phasic pain-evoked GBOs could not only encode pain variability from moment to moment within individuals, but also predict pain sensitivity across different individuals, in both humans and rodents (Figure 1). However, previous publications have also reported substantial heterogeneity in GBO characteristics and functions, and this heterogeneity and its sources have not been clearly described and explored.
To address these issues, Dr. HU's research team conducted a systematic review and meta-analysis to characterize the signal characteristics and summarize the functional significance of GBOs. They found that pain-related GBOs could reflect pain perception in healthy people, and that higher frequency GBOs were induced by phasic pain than tonic pain and chronic pain—a finding consistent across different species (i.e., humans and rodents). Phasic pain-evoked GBOs also seemed to have different neural origins from non-phasic pain-evoked GBOs. Whereas GBOs induced by phasic pain were more centrally distributed, suggesting a sensorimotor origin, GBOs induced by tonic and chronic pain were more frontally distributed over the prefrontal cortex. Moreover, according to previous studies, Dr. HU's research team summarized almost all major functions of GBOs, which differed among phasic, tonic, and chronic pain (Figure 2). These findings suggest that pain-related GBOs should not be considered as a single entity.
This study not only supports GBOs as a candidate pain biomarker, but also provides a systematic description of the heterogeneity of GBO characteristics and functions. Furthermore, this study could serve as an important reference for follow-up research, and lay the foundation for clinical applications of GBOs, which will facilitate the objective assessment and precise treatment of pain.
This work has been published online in Neuroscience & Biobehavioral Reviews, entitled "Gamma-band oscillations of pain and nociception: A systematic review and meta-analysis of human and rodent studies" since Jan 20, 2023. This research was supported by the Beijing Natural Science Foundation and the National Natural Science Foundation of China.
Figure 1 Gamma-band oscillations encode pain sensitivity at both within-subject (a) and between-subject levels (b). Image by HU Li.
Figure 2 Proposed functions of human GBOs. GBOs induced by phasic, tonic, and chronic pain are likely to reflect different functions. Image by HU Li.
LIU Chen
Institute of Psychology
Chinese Academy of Sciences
Beijing 100101, China.
E-mail: liuc@psych.ac.cn
