Based on our understanding that the cerebral evoked potential is a come potential and on thecomputer average principle

we have designed a new method-inverse avge technique

or inverseaddition

for eliminating the components of nonpain sensation from the rebral evoked complexpotentials averaging by the complex sensational stimulations.As a result the pure painful componentscan now be separated from the cerebral evoked complex potentials.There were 30 normal subjects in our observations.The 8 of them

whos somatosensory evokedpotential with W shape were done in a series of experiment.The characteris of the waves of thestrong nonpain stimulation with an approach to the pain threshold subtracting the medium nonpain sti-mulation are:The latency of each of the components is later more or less than the strong nopain stimulationexcept the initial component;the phase of each of the componeuts does no change and the nmplitudeof each component is lessened except the components of latencies later than 300 ms.However the cha-racteristics of the waves of the light pain stimulation subtracting the strong nonpain stimulation (bothpain and nonpain stimulation approach to the pain threshold)are:Compared with pain evoked complex potential the phase of each of the components changes;the late-ncy of each of the components increase except the latency of 170-240 ms

Contrarily

the latenciesdecrease.The summation of this study is till under way.