Many animal studies suggest that during sleep deprivation (SD) synaptic strength should progressively increase, leading to the saturation of the ability to induce long-term potentiation (LTP). Nevertheless, direct evidences about the effects of sustained wakefulness on cortical plasticity in humans are still lacking. The aim of the present study was to assess changes in the ability to induce LTP-like mechanism in humans during a period of SD by means of a paired associative stimulation (PAS) protocol, which combines median nerve stimulation with transcranial magnetic stimulation (TMS) applied over the contralateral somatosensory cortex. During a 41-h SD protocol, 16 healthy subjects, defined as responders to the PAS protocol after a pre-selection session, were involved in 4 experimental sessions (11.00 a.m. and 11.00 p.m. of first and second day) with: a) pre-PAS somatosensory evoked potentials (SEPs) recordings; b) PAS protocol; c) post-PAS SEPs recordings. The effect of PAS on SEPs early components (N20-P25 complex) was assessed. During the first experimental session (without SD) no significant PAS effects on SEPs components amplitude have been found, and large intra- and inter-individual variability have been observed. A lack of significant changes has been observed also in the subsequent sessions. Our results index a low intra- and inter-individual reliability of the PAS protocol, suggesting particular caution when longitudinally evaluating the effect of this technique on cortical plasticity.

中文翻译：

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通过配对联想刺激评估睡眠剥夺过程中的体感皮层可塑性。

许多动物研究表明，在睡眠剥夺（SD）期间，突触强度应逐渐增加，导致诱导长期增强（LTP）的能力达到饱和。然而，仍然缺乏关于持续苏醒对人类皮质可塑性的影响的直接证据。本研究的目的是通过配对联合刺激（PAS）方案评估SD期间人类诱发LTP样机制的能力的变化，该方案结合了中位神经刺激和经颅磁刺激（TMS）应用于对侧体感皮层。在41小时的SD方案中，预选会议后定义为对PAS方案有反应的16位健康受试者参与了4个实验会议（上午11:00和下午11.00）第一天和第二天）：a）PAS之前的体感诱发电位（SEPs）记录；b）PAS协议；c）PAS之后的SEP记录。评估了PAS对SEP早期成分（N20-P25复合物）的影响。在第一个实验阶段（无SD），未发现PAS对SEPs成分振幅有明显影响，并且观察到较大的个体内和个体间变异性。在随后的会议上也观察到缺乏重大变化。我们的研究结果表明，PAS方案在个体内和个体间的可靠性较低，这在纵向评估该技术对皮层可塑性的影响时应特别谨慎。评估了PAS对SEP早期成分（N20-P25复合物）的影响。在第一个实验阶段（无SD），未发现PAS对SEPs成分振幅有明显影响，并且观察到较大的个体内和个体间变异性。在随后的会议上也观察到缺乏重大变化。我们的研究结果表明，PAS方案在个体内和个体间的可靠性较低，这在纵向评估该技术对皮层可塑性的影响时应特别谨慎。评估了PAS对SEP早期成分（N20-P25复合物）的影响。在第一个实验阶段（无SD），未发现PAS对SEPs成分振幅有明显影响，并且观察到较大的个体内和个体间变异性。在随后的会议上也观察到缺乏重大变化。我们的研究结果表明，PAS方案在个体内和个体间的可靠性较低，这在纵向评估该技术对皮层可塑性的影响时应特别谨慎。