The personal experience of pain is quite variable among individuals, even in cases where the underlying injury is identical.
Although previous studies have shown that genetics can influence pain susceptibility, researchers still haven’t developed a reliable tool to help predict patients’ pain levels, particularly after medical interventions such as chemotherapy or surgery.
Now a new study, conducted by researchers at the University of Birmingham (UK) and the University of Maryland, finds that measuring the frequency of a person’s alpha brain waves may help reveal how vulnerable he or she is to developing and experiencing pain. Alpha waves (8 to 12 Hz) are present when the brain is in an idling default-state such as while daydreaming, meditating or practicing mindfulness.
The aim of the study was to see if — based on the resting brain activity of a healthy individual — it were possible to predict how much pain the participant would report once prolonged pain had been induced.
The findings show that participants with a slower frequency of alpha brain waves reported being in much more pain than those who had a faster alpha frequency.
The researchers induced the pain by applying and heating capsaicin paste, an ingredient found in hot chili peppers, to the left forearms of all 21 participants. Topical capsaicin exposure induces “robust thermal hyperalgesia,” a common symptom in chronic pain. All of the volunteers in the study experienced a state of pain for around an hour.
Using an electroencephalogram (EEG) to measure electrical activity of the brain, the researchers discovered that those who had a slower frequency of alpha brain waves recorded before the pain reported being in much more pain than those who had a fast frequency of alpha brain waves.
The researchers also recorded the activity of alpha brain waves during the experience of pain, and if alpha frequency increased (relative to the no-pain condition) the participants reported to be in less pain than when alpha pain decreased.
“Here we observe that an individual’s alpha frequency can be used as a measure of an individual’s predisposition to developing pain,” said co-senior author Dr. Ali Mazaheri, of the University of Birmingham’s Center for Human Brain Health. “This has a direct relevance to understanding what makes an individual prone to chronic pain after a medical intervention, such as surgery or chemotherapy.
“Potentially this means we could be able to identify which individuals are more likely to develop pain as a result of a medical procedure and take steps early on in formulating treatment strategies in patients likely to be predisposed to developing chronic pain.”
Dr. David Seminowicz and graduate student Andrew Furman of the University of Maryland were also authors of the report.
“Alpha frequency has been found to be slower in individuals who have experienced chronic pain. So the fact we observed that the slowing down of alpha activity as a result of pain correlated with the intensity of an individual’s pain report was not that unexpected,” said Furman.
But he said that what was very surprising was that the pain-free alpha frequency, recorded before the onset of pain, could predict how much pain individuals would experience.
“This would suggest that it could be that the slowing of alpha activity in the chronic pain patients isn’t because of the pain, but rather these individuals had slow alpha frequency to begin with, and as such were more prone or vulnerable to developing pain.”
The findings are published in the journal Neuroimage.
Source: University of Birmingham