British researchers have discovered that arthritis pain, unlike that induced as part of an experiment, is processed in the parts of the brain concerned with emotions and fear. (File Photo)

    LONDON, March 30 (Xinhua) -- British researchers have discovered that arthritis pain, unlike that induced as part of an experiment, is processed in the parts of the brain concerned with emotions and fear.

    A research team at The University of Manchester led by Bhavna Kulkarni has captured the first images of how the brain processes arthritis pain, using positron emission tomography (PET) scanners,science news website AlphaGalileo reported on Friday.

    Previous neuro-imaging studies show that experimentally-induced pain is processed in at least two brain networks, collectively known as the 'pain matrix', with the 'medial pain system' processing the emotional aspects such as pain's unpleasantness and the 'lateral pain system' processing the pain's intensity, location and duration.

    The researchers wanted to see whether the same applied to the clinical pain suffered by people with conditions like arthritis, as no direct comparisons of experimental and clinical pain had been undertaken in the same group of patients.

    The researchers compare the brain areas involved in processing arthritic and experimental pain in a group of patients with osteoarthritis. Six female and six male patients with osteoarthritis of the knee underwent PET brain-scanning during three different pain states: arthritic knee pain, experimental knee pain (when no arthritic pain was present) and a pain-free state, with each patient also rating their perceived pain intensity and unpleasantness on 0-100 rating scales at 10 minute intervals.

    Kulkarni said they thought that arthritic and acute experimental pain would be processed within the same areas of the pain matrix, but, although both activated both the medial and lateral pain systems, arthritic pain prompted increased activity in the cingulate cortex, thalamus and amygdale within the medial system -- the areas concerned with processing fear, emotions and aversive conditioning.

    This suggests that arthritic pain has more emotional salience than experimental pain for these patients, which is consistent with the unpleasantness scores they themselves gave, Kulkarni said.

    The finding that both experimental and arthritic pains activate the medial and lateral pain systems suggests that there isn't a unique brain network for processing arthritic pain, according to project supervisor Anthony Jones.

    The study has demonstrated the importance of the medial pain system during the experience of arthritic pain, suggesting it would be a good target for both new analgesics and non-pharmacological interventions.

    The body's own pain-killing chemicals -- the endogenous opioid system -- could even be a possible candidate for modulation to target pain in the areas the researchers have identified.