Figure 1.

Experimental paradigm. Manual acupuncture was administered to LI4, LV3 and ST36 on the right. The subject's sensitivity to needling was pre-tested and adjusted to tolerance prior to scanning. After remaining in place for 2 min (R1), the needle was rotated forward and backward with even motion for 2 min at the rate of 60 times per minute with a amplitude of approximately 180° in each direction (M1). After a rest period of 3 min (R2), needle manipulation was repeated in like manner (M2). The needle was withdrawn 1 minute after completion of acupuncture. For tactile stimulation control, the acupoint was tapped with a size 5.88 von Frey monofilament using a matched paradigm.