Acupuncture and the modulation of cortical excitability.

Although acupuncture is increasingly utilized for medical therapy, its mechanism of action remains uncertain. We used transcranial magnetic stimulation to demonstrate lateralized effects of motor cortex excitability with this technique. Right-sided reduction in motor cortex excitability and a tendency to the opposite effect on the left side was seen with acupuncture. Sham needle insertions did not result in significant changes of motor cortex excitability. These findings provide new neurophysiological evidence of cortical excitability modulation complementary to findings derived from functional neuroimaging studies.