Valls-Solé J, Hallett M, Alvarez R
Departament de Medicina, Universitat de Barcelona, Spain.
Electroencephalogr Clin Neurophysiol. 1996 Dec;101(6):504-10. doi: 10.1016/s0013-4694(96)95697-0.
The technique of paired stimulation is routinely used in many laboratories in the assessment of the excitability recovery curve of the blink reflex. Other effects, such as prepulse inhibition or classical conditioning, can also be investigated with repeated presentation of pairs of time-locked stimuli. Regularly repeated presentations of an unpleasant stimulus may give rise to a transient excitability enhancement in neural structures in the reflex circuit. We have investigated whether such a transient shift in excitability can be demonstrated before the actual stimulus is applied. In 10 normal volunteers, we regularly alternated series of 5 trials containing an auditory tone of mild intensity with series of the same auditory tone followed by a relatively strong supraorbital nerve electrical stimulus. We calculated the habituation percentage of the orbicularis oculi responses to the auditory stimulus within a series and compared the results obtained in series containing the auditory tone alone with those from series containing the auditory tone followed by the electrical stimulus. Habituation was significantly less with paired stimulation than with the auditory tone alone, the mean area of the response to the 3rd trial in percentage of that to the first trial being 34.0 +/- 16.4% for paired stimuli, and 20.3 +/- 14.1% for auditory stimulus alone (P = 0.008). This effect, induced by the presence of an impending electrical stimulus on the response to a preceding stimulus, is defined as a postpulse effect in contradistinction to the prepulse effects induced by a weak stimulus on the response to a subsequent startle-eliciting stimulus. When a paradigm with a stimulus pair is used in human subjects, the possibility of effects occurring in both temporal directions should be taken into account. Blink reflex responses to a given stimulus may exhibit excitability changes induced by a preceding or by an impending stimulus.
配对刺激技术在许多实验室中经常用于评估瞬目反射的兴奋性恢复曲线。其他效应，如前脉冲抑制或经典条件反射，也可以通过重复呈现成对的锁时刺激来进行研究。定期重复呈现不愉快刺激可能会导致反射回路中神经结构的短暂兴奋性增强。我们研究了在实际刺激应用之前是否能证明这种兴奋性的短暂变化。在10名正常志愿者中，我们定期交替进行包含轻度强度听觉音调的5次试验系列与相同听觉音调后接相对较强眶上神经电刺激的系列试验。我们计算了一系列试验中眼轮匝肌对听觉刺激反应的习惯化百分比，并比较了仅包含听觉音调的系列试验结果与包含听觉音调后接电刺激的系列试验结果。配对刺激时的习惯化明显低于仅用听觉音调时，配对刺激时第3次试验反应面积相对于第1次试验的平均百分比为34.0±16.4%，仅听觉刺激时为20.3±14.1%（P = 0.008）。由即将到来的电刺激对先前刺激反应的影响所诱导的这种效应，与弱刺激对随后引发惊吓刺激反应所诱导的前脉冲效应相反，被定义为后脉冲效应。当在人类受试者中使用刺激对范式时，应考虑在两个时间方向上都可能出现效应的可能性。对给定刺激的瞬目反射反应可能会表现出由先前或即将到来的刺激所诱导的兴奋性变化。
