长期以来

人们希望能对疼痛感受有一个客观指标

然而一直未能解决。人体实验性疼痛的测定

由于缺少客观测量方法而受到阻碍。自从Dawson创立了累加技术

为在人体无创伤地记录脑诱发电位提供了可能。近年来累加体感诱发反应的研究

为实The developm ent in the study of the cerebral-pain evoked potential has pointed out a way for evaluation of experimental pain. The components of early response(latency about 30 ms)and late response(latency about 160-206 ms)in the cerebral-pain evoked potential were closely related to pain perception. But these studies could not rule out the action of non-pain sensation

such as touch

pressure

temperature etc. So far

we have not seen any report on pure painful components of cerebral evoked potentials. Based on our understanding that the cerebral evoked potential is a complex potential and on the computer average principle

we have designed a new method

inverse average technique

for eliminating the components of nonpain sensation from the cerebral evoked complex potentials. The inverse average technique is a very useful method. It will be reported in another paper. 30 normal subjects were observed. Result: The direct and the inverse cerebral evoked complex potentials elicited by the same stimulation were inversely averaged

producing the inverse-averaged potential. All components of inverse averaged potential offset except the highest amplitude component of cerebral evoked complex potential

1.3% of which remained. The most remains did not exceed by 9%. A series of experiments were done on 8 of these subjects whose somatosensory evoked potential showed a w shape. Three stimulations with different intensity were applied. They were medium nonpain stimulation—mean 75 V

strong nonpain stimulation—mean 114 V

and light pain stimulation—mean 156 V. The strong non-pain stimulation and light dain stimulation approached the pain threshold. The wave characteristics of the strong non-pain stimulation were: The latency of each of the components was more or less longer than that of strong non-pain stimulation except the initial component; the phase of each of the components did not change and the amplitude of each component was smaller except the components with latencies of more than 300 ms. The characteristics of the waves of the light pain stimulation subtracting the strong non-pain stimulation(both pain and non-pain stimulations approaching the pain threshold)were: Compared with the pain evoked complex potential the phase of each of the components changed; the latency of each of the components increased except the latency of 170-240 ms which contrarily decreased. This technique and results have provided a new way of study for the evaluation of experimental pain in human and for the coding of nervous information.