疼痛是大脑编码和处理伤害性刺激,避免潜在的或实际的组织损伤的一种保护功能.人体内传导伤害性信息的神经纤维主要有Aδ和C纤维.伤害性信息经过这两类纤维的传导和大脑结构的多重加工,最终产生人体的一次快疼痛和二次慢疼痛.较强烈的激光辐射热脉冲可选择性激活皮肤浅表层中的伤害性游离神经末梢,诱发脑电(electroencephalography,EEG)活动的变化,即激光诱发电位(laser-evoked potentials,LEPs).至今,研究者共挖掘出Aδ-LEPs的6个稳定成分,即时域上的Aδ-N1,Aδ-N2,Aδ-P2,Aδ-P4波,时频域上神经振荡节律成分alpha频段的事件相关去同步化(event-related desynchronization,α-ERD)和gamma频段的事件相关同步化(event-related synchronization,γ-ERS).与此同时,研究者优化了C-LEPs提取的实验范式和参数,获得了2个稳定成分,即时域上的C-N2,C-P2波.本文详述了LEPs相关的神经电生理特征及其认知功能.LEPs既能帮助我们探究伤害性感觉输入的外周和中枢加工机制,在疼痛临床研究中有重要价值,也能为某些基础研究(如老龄化问题和社会认知等)提供新的手段.
Pain is related to the encoding and processing of afferent nociceptive information in the brain, and is a critical factor that allows humans and animals to learn to avoid potential or actual tissue injury. Being conducted by A5 fibers and C fibers, nociceptive signals are processed by multiple brain structures, and normally generate a double sensation: an initial pricking pain (first pain) and a prolonged burning sensation (second pain). Intense laser heat pulses can selectively excite nociceptive free nerve endings in superficial layers of the skin. Such stimuli can elicit changes in brain responses (laser-evoked potentials, LEPs) in the ongoing electroencephalograms (EEGs). Until now, six reliable components have been detected in AS-LEPs: AS-N1, AS-N2, AS-P2, and AS-P4 waves in the time domain and alpha-band event-related desynchronization (α-ERD) and gamma-band event-related synchronization (γ-ERS) in the time- frequency domain. Meanwhile, by optimizing the experimental paradigm and parameters, two components of C-LEPs have been reliably detected: C-N2 and C-P2 waves in the time domain. The present paper reviewed the neural electrophysiological features of LEPs and their cognitive significance. LEPs can not only be used to investigate the peripheral and central processing of nociceptive sensory input, which is important in several clinical applications, but also be adopted in some basic research (e.g., the aging problem and social cognition) as a novel neurophysiological technique.