Center for Interdisciplinary Research in Rehabilitation and Social Integration (CIRRIS), Québec, QC, Canada.
Center for Interdisciplinary Research in Rehabilitation and Social Integration (CIRRIS), Québec, QC, Canada; Department of Rehabilitation, Laval University, Québec, QC, Canada.
Neuroimage. 2020 Aug 1;216:116883. doi: 10.1016/j.neuroimage.2020.116883. Epub 2020 Apr 27.
Temporal predictability and intensity of an impending nociceptive input both shape pain experience and modulate laser-evoked potentials (LEPs) amplitude. However, it remains unclear whether and how these two factors could influence pain-induced corticospinal excitability modulation. The current study investigated the influence of nociceptive stimulation intensity and temporal predictability on motor-evoked potentials (MEPs) modulation, in parallel to their effect on pain perception and LEPs amplitude. Twenty participants completed electroencephalographic and transcranial magnetic stimulation experiments during which two laser nociceptive stimulation intensities (high and low) were either unpredictably delivered (random delay) or preceded by a fixed-timing cue (fixed delay). The amplitude of the conditioned MEPs was significantly reduced only for the high nociceptive stimulation and was not affected by the temporal predictability of pain (despite the fact that temporal predictability modulated the amplitude of P2 LEP component amplitude). However, a posteriori analyses based on patterns of pain-induced MEPs modulation revealed that participants in which nociceptive stimulation resulted in an increase in corticospinal excitability were more affected by the predictability of pain (i.e. increasing corticospinal excitability even more when pain occurrence was predictable), regardless of the nociceptive stimulation intensity; whereas participants in which nociceptive stimulation resulted in a decrease in corticospinal excitability were sensitive to the intensity of the stimulation but not its predictability. These results suggest a potential influence of cognitive factors such as temporal predictability on the response of the motor system in the presence of pain for some participants, contributing to explain, at least in part, the high variability highlighted in a number of previous studies.
即将到来的伤害性输入的时间可预测性和强度都会影响疼痛体验，并调节激光诱发电位（LEP）的振幅。然而，目前尚不清楚这两个因素是否以及如何影响疼痛引起的皮质脊髓兴奋性调节。本研究同时考察了伤害性刺激强度和时间可预测性对运动诱发电位（MEPs）调制的影响，以及它们对疼痛感知和 LEP 振幅的影响。20 名参与者在进行脑电图和经颅磁刺激实验时，接受了两种不同强度的激光伤害性刺激（高强度和低强度），这些刺激要么是不可预测地（随机延迟）给予的，要么是由固定定时线索（固定延迟）预先给予的。只有高强度的伤害性刺激才会显著降低条件性 MEPs 的振幅，而疼痛的时间可预测性不会影响其振幅（尽管时间可预测性调节了 P2 LEP 成分振幅）。然而，基于疼痛诱导的 MEPs 调制模式的事后分析表明，伤害性刺激导致皮质脊髓兴奋性增加的参与者更容易受到疼痛可预测性的影响（即当疼痛发生可预测时，甚至会进一步增加皮质脊髓兴奋性），而与伤害性刺激强度无关；而伤害性刺激导致皮质脊髓兴奋性降低的参与者对刺激强度敏感，但对其可预测性不敏感。这些结果表明，对于一些参与者来说，认知因素（如时间可预测性）可能会对疼痛存在时运动系统的反应产生潜在影响，这至少可以部分解释之前许多研究中强调的高度变异性。
