A topographic observation using 128 channal electric signal imaging system on early components(N20 and following 20ms) of sensory evoked potential (SEP) was carried out on ten subjects after stimulating acupoints of the Three-Yin Meridians of the Hand. Results showed when acupoint was stimulated

high voltage areas were ohserved not only in S I area but also in other regions of the cere-bral cortex

having a dynamic changlng process

this indicates there is a complicated cortical mechanism in percepting information of acupuncture. Comparing the opographic maps of SEP induced by acupuncture at different acupoints

a general similar spatiotemporal changing process of electric activity could be found and several cortical reglons

such as frontal

central

occipital and post-temporal are in-volved. All of these results .provide a new clue for us to find out the mechanism of acupunture.