Sleep behaviour and memory consolidation in patients with disorders of consciousness

睡眠-觉醒周期的存在是一个鉴别诊断标准，标志着从昏迷过渡到无反应觉醒综合征（UWS）和最低意识状态（MCS）。由于许多研究都发现睡眠对记忆痕迹的巩固有积极作用，而且这种作用的机制也很大程度上是已知的，所以问题是睡眠对学习的这种有益作用是否也能在UWS和MCS患者中得到证明（如果是的话，也许它可以用于这些患者的康复）。然而，为了研究这个问题，我们首先要(1)描述UWS和MCS的睡眠生理结构，因为它与健康个体的睡眠生理结构有很大的不同；(2)详细阐述他们的睡眠评分标准，因为由于睡眠结构异常，现有的标准不能在不调整的情况下应用；(3)开发特定的学习任务，因为睡眠/记忆实验中标准使用的任务不能应用于行为无反应的患者。所有这些目标在该项目的第一阶段已经实现。现在，在第二阶段，我们计划测试睡眠支持UWS和MCS记忆巩固的假设。在受试者内设计中，患者将被提供三个平衡条件：1睡眠条件：学习任务=>间隔5h睡眠=>任务重新测试2清醒条件：学习任务=>间隔5h睡眠=>任务重新测试3控制条件：间隔5h睡眠=>学习任务（在5小时之前没有任务）控制条件是必要的，以区分记忆巩固的可能效果和觉醒期间治疗干预的效果。与睡眠条件下的第一次任务呈现相比，我们期望在重测时的任务表现有显著提高。此外，这种改善预计与特定的睡眠成分（如纺锤波）和患者的神经心理状态有关。

The presence of sleep-wakefulness cycles is a differential diagnostic criterion marking the transition from coma to Unresponsive Wakefulness Syndrome (UWS) and Minimally Conscious State (MCS). Because a positive effect of sleep on the consolidation of memory traces was found in numerous studies and the mechanisms of the effect are largely known, a question arises whether such beneficial effect of sleep on learning can also be demonstrated in UWS and MCS patients (and if yes, perhaps it can be used in these patients’ rehabilitation). However, to investigate this issue, we had first (1) to describe the physiological structure of sleep in UWS and MCS, as it strongly differs from that in healthy individuals, (2) to elaborate criteria for their sleep scoring, as the extant criteria cannot be applied without adjustment due to the abnormal sleep structure, and (3) to develop specific learning tasks, as the tasks standardly used in sleep/memory experiments cannot be applied in behaviorally non-responsive patients.All these aims have been attained in the first period of this project. Now, in the second phase we plan to test the hypothesis that sleep supports memory consolidation in UWS and MCS. In a within-subject design, patients will be presented three counterbalanced conditions:1 Sleep Condition: Learning Task => 5h interval with sleep => Task Retest2 Wakefulness Condition: Learning Task => 5h interval w/out sleep => Task Retest3 Control Condition: 5h period w/out sleep => Learning Task (no task before the 5h period)The control condition is necessary to disentangle the possible effect of memory consolidation from the effect of therapeutic intervention during wakefulness period. We expect significantly better task performance at retest as compared with the first task presentation in the Sleep Condition. Furthermore, this improvement is expected to correlate with specific sleep components (e.g., spindles) and with the patient’s neuropsychological state.