Tavakoli Paniz, Dale Allyson, Boafo Addo, Campbell Kenneth
Children's Hospital of Eastern Ontario, Ottawa, ON, Canada.
School of Psychology, University of Ottawa, Ottawa, ON, Canada.
Front Neurosci. 2019 Jan 10;12:1028. doi: 10.3389/fnins.2018.01028. eCollection 2018.
The present study examines processes associated with intrusions into consciousness during an unconscious state, natural sleep. The definition of sleep is still much debated. Almost all researchers agree that sleep onset represents a gradual loss of consciousness of the external environment. For sleep to be beneficial, it needs to remain as undisturbed as possible. Nevertheless, unlike other unconsciousness states, sleep is reversible. For purposes of survival, it is critical that the sleeper be able to "detect" and perhaps become conscious of highly relevant biological or personal information. Therefore, even in sleep, the brain must decide whether a new incoming stimulus is relevant and if so, may require an arousal to wakefulness, or whether it is irrelevant and can be gated to prevent disruption of sleep. Event-related potentials (ERPs) were used to measure the extent processing of auditory stimuli some of which elicited an ERP component, the P3a, in the waking state. The P3a is associated with processes resulting in the interruption of frontal central executive, leading to conscious awareness. Very little research has focused on the occurrence of the P3a during sleep. A multi-feature paradigm was used to examine the processing of a frequently occurring "standard" stimulus and six rarely occurring different "deviant" stimuli during wakefulness, NREM, and REM sleep. A P3a was elicited by novel environmental sounds and white noise bursts in the waking state, replicating previous studies. Other deviant stimuli (changes in pitch, intensity, duration) failed to do so. The ERPs indicated that processing of the stimuli that did not elicit a P3a in wakefulness were much inhibited during both NREM and REM sleep. Surprisingly, those deviants that did elicit a P3a in wakefulness continued to do so in stage N2 and REM sleep. The subject did not, however, awaken. These results suggest processes leading to consciousness in wakefulness may still remain active during sleep possibly allowing subjects to act on potentially highly relevant input. This may also explain how sleep can be reversed if the stimulus input is sufficiently critical.
本研究考察了在无意识状态即自然睡眠期间侵入意识的相关过程。睡眠的定义仍存在诸多争议。几乎所有研究者都认同，睡眠开始意味着对外界环境意识的逐渐丧失。为使睡眠有益，它需要尽可能保持不受干扰。然而，与其他无意识状态不同，睡眠是可逆的。为了生存，睡眠者能够“检测”并可能意识到高度相关的生物或个人信息至关重要。因此，即使在睡眠中，大脑也必须判定新传入的刺激是否相关，如果是，可能需要唤醒至清醒状态，或者判定它是否不相关并可被阻止以防止睡眠中断。事件相关电位（ERP）被用于测量听觉刺激的处理程度，其中一些听觉刺激在清醒状态下引发了ERP成分P3a。P3a与导致额叶中央执行功能中断并引发意识觉知的过程相关。很少有研究关注睡眠期间P3a的出现情况。采用多特征范式来考察在清醒、非快速眼动（NREM）睡眠和快速眼动（REM）睡眠期间，对频繁出现的“标准”刺激以及六种很少出现的不同“偏差”刺激的处理情况。在清醒状态下，新的环境声音和白噪声脉冲引发了P3a，这与先前的研究结果一致。其他偏差刺激（音高、强度、持续时间的变化）则未能引发P3a。ERP结果表明，在清醒状态下未引发P3a的刺激在NREM和REM睡眠期间的处理都受到了极大抑制。令人惊讶的是，那些在清醒状态下引发P3a的偏差刺激在N2期和REM睡眠中仍能引发P3a。然而，受试者并未醒来。这些结果表明，在清醒状态下导致意识产生的过程在睡眠期间可能仍然活跃，这可能使受试者能够对潜在高度相关的输入做出反应。这也可以解释，如果刺激输入足够关键，睡眠如何能够被逆转。
