It is still not clear what role is played by cortical somatosensory system during the advance of propagated sensation along meridians (PSM).In this paper the short-latent somatosensory evoked potential (SLSEP) was taken as an indication to observe the characteristics of functional activity in cortical soma- tosensory area I (SI) during the advance of PSM. The observation was preformed on 10 subjects with marked PSM

which were clear and kept stable.Sixteen subjects without SPM were taken as cont- rol.Electrical stimulation was delivered to the acupoint Jiaxi (GB43) or Hegu (LI4).The SLSEP were recorded simultaneously from 3 scalp points corres- ponding to the representative areas of foot

arm and face contralateral to the stimulated side.The results are shown as follows. When Jiaxi was stimulated

the amplitudes of SLSEP component C_2 (P_(45)- N_(55)) from above three scalp points in subjects without PSC were 0.85±0.17

0.51±0.11 and 0.31±0.07μv respectively.The amplitude was largest in the foot representative area

but attenuated successively in arm and face areas and a stair-shaped distributiou was thus formed.During stimulating the acupoint Hegu (LI4) the amplitude of SLSEP component C_2 (P_(25)-N_(55)) from the repre- sentative area of arm in subjects without PSM was larger than that from the represeutative areas of foot and face

and a distribution with high-medium and low-bilateral character was shaped.However

no matter whether stimulating Jiaxi or Hegu the amplitude of SLSEP C_2 in subjects with marked PSM was nearly the same from three scalp points. The results suggest that the extensive excitation appeared in various repre- sentative areas of S1 in subjects with marked PSM and they might be more su- sceptible to the stimulation of acupoints.Perhaps

this is one of the favoura- ble condition for the formation of PSM.