These findings could spur a new direction in the field of acupuncture research following recent controversy over large studies showing that sham acupuncture is as effective as real acupuncture in reducing chronic pain.

'Interestingly both acupuncture and sham acupuncture groups had similar reductions in clinical pain,' Harris said. 'But the mechanisms leading to pain relief are distinctly different.'

The study participants included 20 women who had been diagnosed with fibromyalgia, a chronic pain condition, for at least a year.

The results appeared online ahead of print in the September issue of the Journal of NeuroImage.