Study gives clues about the location of chronic pain in the brain – 05/23/2023 – Equilibrium

Researchers have for the first time recorded the brain’s firing patterns when a person experiences chronic pain, paving the way for devices implanted in the future to predict pain signals or even short-circuit them.

Using a pacemaker-like device surgically placed inside the brain, the scientists recorded four patients who experienced uninterrupted nerve pain for over a year. The devices recorded multiple times a day for up to six months, offering clues to where chronic pain resides in the brain.

The study, published on Monday (22) in the journal Nature Neuroscience, reported that pain was associated with electrical fluctuations in the orbitofrontal cortex, an area involved in emotional regulation, self-assessment and decision-making. Research suggests these patterns of brain activity could serve as biomarkers to guide the diagnosis and treatment of millions of people with stabbing or chronic burning pain linked to a damaged nervous system.

In the study, Prasad Shirvalkar, a neurologist at the University of California, San Francisco, and his colleagues used electrodes to measure the collective firing pattern of thousands of neurons in close proximity to the electrodes.

The researchers surgically implanted the recording devices in four people who had been living with pain for over a year and were not finding relief from medication. For three of the patients, the pain started after a stroke (cerebrovascular accident). The fourth had so-called phantom limb pain after losing a leg.

At least three times a day, patients rated their pain and then pressed a button that stimulated their implants to record brain signals for 30 seconds.

The researchers placed electrodes in two areas of the brain: the orbitofrontal cortex, which has not been studied much in pain research, and the anterior cingulate cortex, a region involved in processing emotional signals.

The scientists fed data from patients’ pain scores and corresponding electrical signals into machine learning models, which could predict high and low chronic pain states based on brain signals alone.

The researchers found that certain frequency fluctuations in the orbitofrontal cortex were the best predictors of chronic pain. While this brain signature is common among patients, Shirvalkar said, each of them also showed unique brain activity.

“Each patient really had a different fingerprint for their pain,” he said.

Translated by Luiz Roberto M. Gonçalves