Department of Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany.
Cereb Cortex. 2012 Feb;22(2):426-35. doi: 10.1093/cercor/bhr121. Epub 2011 Jun 13.
Nonrapid eye movement (NREM) sleep is characterized by periodic changes in cortical excitability that are reflected in the electroencephalography (EEG) as high-amplitude slow oscillations, indicative of cortical Up/Down states. These slow oscillations are thought to be involved in NREM sleep-dependent memory consolidation. Although the locus coeruleus (LC) noradrenergic system is known to play a role in off-line memory consolidation (that may occur during NREM sleep), cortico-coerulear interactions during NREM sleep have not yet been studied in detail. Here, we investigated the timing of LC spikes as a function of sleep-associated slow oscillations. Cortical EEG was monitored, along with activity of LC neurons recorded extracellularly, in nonanesthetized naturally sleeping rats. LC spike-triggered averaging of EEG, together with phase-locking analysis, revealed preferential firing of LC neurons along the ascending edge of the EEG slow oscillation, correlating with Down-to-Up state transition. LC neurons were locked best when spikes were shifted forward ∼50 ms in time with respect to the EEG slow oscillation. These results suggest that during NREM sleep, firing of LC neurons may contribute to the rising phase of the EEG slow wave by providing a neuromodulatory input that increases cortical excitability, thereby promoting plasticity within these circuits.
非快速眼动 (NREM) 睡眠的特征是皮质兴奋性的周期性变化，在脑电图 (EEG) 中表现为高振幅慢波，表明皮质上/下状态。这些慢波被认为参与了 NREM 睡眠依赖性记忆巩固。尽管蓝斑核 (LC) 去甲肾上腺素能系统被认为在离线记忆巩固中发挥作用（可能发生在 NREM 睡眠期间），但 NREM 睡眠期间皮质-蓝斑核相互作用尚未得到详细研究。在这里，我们研究了 LC 尖峰的时间作为睡眠相关慢波的函数。在非麻醉自然睡眠的大鼠中，监测皮质 EEG 以及细胞外记录的 LC 神经元活动。LC 尖峰触发 EEG 平均，以及相位锁定分析，揭示了 LC 神经元沿 EEG 慢波上升沿的优先放电，与下到上状态转换相关。当尖峰相对于 EEG 慢波向前移动约 50 毫秒时，LC 神经元的锁定最佳。这些结果表明，在 NREM 睡眠期间，LC 神经元的放电可能通过提供增加皮质兴奋性的神经调制输入，从而促进这些回路中的可塑性，来促进 EEG 慢波的上升相。
