Acetylcholine is a neurotransmitter and neuromodulator involved in a variety of cognitive functions. Additionally, acetylcholine is involved in the regulation of REM sleep: cholinergic neurons in the brainstem and basal forebrain project to and innervate wide areas of the cerebral cortex, and reciprocally interact with other neuromodulatory systems, to produce the sleep-wake cycle and different sleep stages. Consciousness and cognition vary considerably across and within sleep stages, with metacognitive capacity being strikingly reduced even during aesthetically and emotionally rich dream experiences. A notable exception is the phenomenon of lucid dreaming—a rare state whereby waking levels of metacognitive awareness are restored during sleep—resulting in individuals becoming aware of the fact that they are dreaming. The role of neurotransmitters in these fluctuations of consciousness and cognition during sleep is still poorly understood. While recent studies using acetylcholinesterase inhibitors suggest a potential role of acetylcholine in the occurrence of lucid dreaming, the underlying mechanisms by which this effect is produced remains un-modelled and unknown; with the causal link between cholinergic mechanisms and upstream psychological states being complex and elusive. Several theories and approaches targeting the association between acetylcholine and metacognition during wakefulness and sleep are highlighted in this review, moving through microscopic, mesoscopic and macroscopic levels of analysis to detail this phenomenon at several organisational scales. Several exploratory hypotheses will be developed to guide future research towards fully articulating how metacognition is affected by activity at the acetylcholine receptor.

乙酰胆碱是一种神经递质和神经调节剂，参与多种认知功能。此外，乙酰胆碱还参与快速眼动睡眠的调节：脑干和基底前脑中的胆碱能神经元投射并支配大脑皮层的广泛区域，并与其他神经调节系统相互作用，产生睡眠-觉醒周期和不同的睡眠阶段。意识和认知在睡眠阶段和睡眠阶段内差异很大，即使在审美和情感丰富的梦境体验中，元认知能力也会显着降低。一个值得注意的例外是清醒梦现象——一种罕见的状态，清醒时的元认知意识水平在睡眠期间恢复——导致个体意识到他们正在做梦的事实。神经递质在睡眠期间意识和认知波动中的作用仍然知之甚少。虽然最近使用乙酰胆碱酯酶抑制剂的研究表明乙酰胆碱在清醒梦的发生中具有潜在作用，但产生这种作用的潜在机制仍未建模和未知。胆碱能机制与上游心理状态之间的因果关系复杂且难以捉摸。本综述重点介绍了几种针对清醒和睡眠期间乙酰胆碱与元认知之间关联的理论和方法，通过微观、中观和宏观层面的分析，在多个组织尺度上详细说明了这一现象。将开发几个探索性假设来指导未来的研究，以充分阐明元认知如何受到乙酰胆碱受体活性的影响。