Beydoun A, Morrow T J, Shen J F, Casey K L
Department of Neurology, University of Michigan Medical School, Ann Arbor.
Electroencephalogr Clin Neurophysiol. 1993 May-Jun;88(3):173-81. doi: 10.1016/0168-5597(93)90002-7.
We recorded laser-evoked potentials (LEPs) from 20 normal subjects by stimulating the skin with pulses from an infrared CO2 laser. The conduction velocity of the peripheral afferent fibers mediating the LEPs averaged 14.9 m/sec. The amplitude of the LEP components correlated significantly with perceived stimulus intensity. During repetitive constant intensity stimulation, the peak-to-peak LEP amplitude decreased 38% during a distraction task and 42% during drowsiness and was absent during stage 2 sleep, indicating a modulation of responsiveness to laser stimulation during distraction and decreased states of arousal. Normative data revealed considerable intersubject variability in LEP latencies and amplitudes. Analysis of intrasubject lateralized (side-to-side) differences revealed that the relative peak-to-peak amplitude was less variable than that of the N or P components. For clinical applications using 3 S.D.s to define the normal range, a lateral interpeak amplitude difference greater than 28% would suggest focal or lateralized sensory abnormality in an individual patient. Vigilance and attentiveness to the stimuli should be monitored during the acquisition of LEPs.
我们通过用红外二氧化碳激光脉冲刺激皮肤，记录了20名正常受试者的激光诱发电位（LEP）。介导LEP的外周传入纤维的传导速度平均为14.9米/秒。LEP成分的幅度与感知到的刺激强度显著相关。在重复性恒定强度刺激期间，在分心任务期间，峰峰值LEP幅度下降了38%，在困倦期间下降了42%，在第二阶段睡眠期间则消失，这表明在分心和唤醒状态降低期间，对激光刺激的反应性受到调制。标准数据显示，LEP潜伏期和幅度在受试者之间存在相当大的变异性。对受试者内部的侧化（左右）差异分析表明，相对峰峰值幅度的变异性小于N或P成分。对于使用3个标准差来定义正常范围的临床应用，两侧峰间幅度差异大于28%可能提示个体患者存在局灶性或侧化感觉异常。在记录LEP期间，应监测对刺激的警觉性和注意力。
