For the first time, scientists, including one of India-origin, have recorded pain-related data from inside the brain of individuals with chronic pain disorders.

In the study, published in the journal Nature Neuroscience, they identified an area of the brain associated with chronic pain and objective biomarkers of chronic pain in individual patients.

Identifying such a pain signature will enable the development of new therapies that can alter brain activity to relieve suffering due to chronic pain, said the researchers.

"When you think about it, pain is one of the most fundamental experiences an organism can have," said lead author Prasad Shirvalkar, Associate Professor of anaesthesia and neurological surgery at the University of California, San Francisco.

"Despite this, there is still so much we don't understand about how pain works. By developing better tools to study and potentially affect pain responses in the brain, we hope to provide options to people living with chronic pain conditions."

For the study, the team looked directly at changes in brain activity in two regions where pain responses are thought to occur -- the anterior cingulate cortex (ACC) and the orbitofrontal cortex (OFC) -- as participants reported their current levels of chronic pain.

Four participants, three with post-stroke pain and one with phantom limb pain were surgically implanted with electrodes targeting their ACC and OFC.

"Functional MRI studies show that the ACC and OFC regions of the brain light up during acute pain experiments. We were interested to see whether these regions also played a role in how the brain processes chronic pain," said Dr. Shirvalkar.

"We were most interested in questions like how pain changes over time, and what brain signals might correspond to or predict high levels of chronic pain?"

Several times a day, each participant was asked to answer questions related to how they would rate the pain they were experiencing, including strength, type of pain, and how their level of pain was making them feel emotional.

They would then initiate a brain recording by clicking a remote-control device, which provided a snapshot of the activity in the ACC and OFC at that exact moment.

Using machine learning analyses, the research team was able to use activity in the OFC to predict the participants' chronic pain state.

In a separate study, the researchers looked at how the ACC and OFC responded to acute pain, which was caused by applying heat to areas of the participants' bodies.

In two of the four patients, brain activity could again predict pain responses, but in this case, the ACC appeared to be the region most involved. This suggests that the brain processes acute vs. chronic pain differently, though more studies are needed given that data from only two participants were used in this comparison.