Brain scans reveal why some people feel your pain

May 31, 2011 | Source: New Scientist Life

Researchers at Monash University in Melbourne, Australia, have observed atypical neurophysiological activity in amputees who experience synesthetic pain (pain synesthetes) when observing pain in another.

The researchers found that reduced alpha and theta brainwaves in pain synesthetes may reflect inhibition of normal inhibitory mechanisms (neurotransmitters involved in the processing of observed pain) as well as increased synesthetic pain.

The researchers used EEG to record brain activity in eight amputees who experienced both phantom and synesthetic pain, 10 amputees who experienced just phantom pain, and 10 healthy people with no amputations while they looked at images of hands or feet in potentially painful and non-painful situations.

When viewing the images, the researchers found that the pain synesthetes exhibited decreased theta and alpha brainwaves compared with the other volunteers.  The researchers said that such a decrease reflects an increase in neural activity, suggesting that their mirror systems (neurons that fire when an animal observes the same action performed by another) are activated more strongly.

They said the traumatic experience associated with losing a limb may heighten the sensitivity of pain synesthetes to others’ pain. When threatened, our body naturally becomes hypervigilant to pain: our pain threshold lowers, which can make even small triggers painful. Pain synesthesia may be a symptom of an abnormal, ongoing hypervigilance, the researchers said.

Ref: Bernadette M. Fitzgibbon, et al., Atypical electrophysiological activity during pain observation in amputees who experience synaesthetic pain, Social Cognitive and Affective Neuroscience, DOI: 10.1093/scan/nsr016