新异刺激模型中的痛觉诱发电位

目的：观察消除了某些心理因素影响后的痛觉诱发电位，以便进一步研究人类疼痛的中枢机制。方法：采用新异刺激(oddball)实验设计来产生痛觉诱发电位。14名被试右手中指给予两种不同强度的电刺激(中等程度的非痛刺激和疼痛刺激)，在两次实验中，分别将两种刺激之一作为新异靶刺激，而将男一种作为标准刺激，记录诱发电位，并比较作为新异靶刺激的疼痛刺激(25Pa)与作为标准刺激的疼痛刺激(75Pa)诱发电位的差异。结果：在数据合格的11名被试中，Cz电极位置25Pa的诱发电位成份与75Pa的诱发电位成份一致，均包括N1、P1、N2三个主要成份，其中25Pa诱发电位N1和P1成份的波幅显著高于75Pa相应成份，而N2成份的波幅在两种疼痛刺激中并无显著差异，两种刺激之间各成份的潜伏期也无统计学差异。偶极子起源分析表明，N1、P1、N2这三个成份可能分别来源于前扣带回、旁中央小叶及扣带回后部。结论：新异刺激设计所得的痛觉诱发电位(75Pa)排除了由疼痛评分及注意等因素所引发的非痛觉特异性认知相关成份，故可更为客观地评价疼痛。

PAIN-EVOKED POTENTIALS IN AN ODDBALL DESIGN

Objective: To eliminate the psychological influence on pain evoked potential and get further access of human central mechanisms of pain. Methods: An oddball design was adopted. Fourteen human subjects were recruited. Electric stimuli of two different intensities (moderate non-pain and moderate pain, respectively) were delivered to the middle finger of the right hands via surface electrodes. Electroencephalographic (EEG) signals were recorded concurrently with stimulation markers. Each subject accepted two experimental sessions. In one session, painful stimuli were set as the oddball target and non-painful stimuli as the standard. In the other session, the design was reversed. Evoked potentials of painful target (25Pa) and pain standard (75Pa) stimulation were compared. Result: In the 11 subjects with qualified data, three components of pain-evoked potentials were identified in vertex Cz site, i.e., N1, P1, and N2, for both 25Pa and 75Pa stimuli. Statistical analysis showed that the amplitudes of 25Pa at Cz/N1 and Cz/P1 were significantly larger than those of 75Pa, while no statistical difference was found for Cz/N2. Single dipole modeling identified their likely source as dorsal anterior cingulate cortex for N1, paracentral lobule for P1 and posterior cingulate cortex for N2. Conclusion: Pain evoked potential in this oddball design (75Pa in particular) are more switable for objective evaluation of pain.