The hippocampus plays a critical role in sleep-related memory processes [1-3], but it is unclear which specific sleep features are dependent upon this brain structure. The examination of sleep physiology in patients with focal bilateral hippocampal damage and amnesia could supply important evidence regarding these links. However, there is a dearth of such studies, despite these patients providing compelling insights into awake cognition [4, 5]. Here, we sought to identify the contribution of the hippocampus to the sleep phenotype by characterizing sleep via comprehensive qualitative and quantitative analyses in memory-impaired patients with selective bilateral hippocampal damage and matched control participants using in-home polysomnography on 4 nights. We found that, compared to control participants, patients had significantly reduced slow-wave sleep-likely due to decreased density of slow waves-as well as slow-wave activity. In contrast, slow and fast spindles were indistinguishable from those of control participants. Moreover, patients expressed slow oscillations (SOs), and SO-fast spindle coupling was observed. However, on closer scrutiny, we noted that the timing of spindles within the SO cycle was delayed in the patients. The shift of patients' spindles into the later phase of the up-state within the SO cycle may indicate a mismatch in timing across the SO-spindle-ripple events that are associated with memory consolidation [6, 7]. The substantial effect of selective bilateral hippocampal damage on large-scale oscillatory activity in the cortex suggests that, as with awake cognition, the hippocampus plays a significant role in sleep physiology, which may, in turn, be necessary for efficacious episodic memory.

中文翻译：

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睡觉时海马体受损。


海马体在睡眠相关的记忆过程中发挥着关键作用 [1-3]，但尚不清楚哪些特定的睡眠特征取决于这种大脑结构。对双侧海马局部损伤和遗忘症患者的睡眠生理学检查可以为这些联系提供重要证据。然而，尽管这些患者对清醒认知提供了令人信服的见解，但此类研究仍很缺乏 [4, 5]。在这里，我们试图通过对选择性双侧海马损伤的记忆受损患者和使用家庭多导睡眠图的匹配对照参与者进行全面的定性和定量分析来描述睡眠特征，从而确定海马对睡眠表型的贡献。我们发现，与对照组参与者相比，患者的慢波睡眠（可能是由于慢波密度降低）以及慢波活动显着减少。相比之下，慢速和快速纺锤体与对照参与者的纺锤体无法区分。此外，患者表现出慢振荡（SOs），并且观察到SO-快纺锤体耦合。然而，经过更仔细的审查，我们注意到患者 SO 周期内纺锤体的时间被延迟。患者的纺锤体转变为 SO 周期内上升状态的后期阶段可能表明与记忆巩固相关的 SO 纺锤体纹波事件的时间不匹配 [6, 7]。选择性双侧海马体损伤对皮质大规模振荡活动的显着影响表明，与清醒认知一样，海马体在睡眠生理学中发挥着重要作用，而这反过来可能是有效的情景记忆所必需的。