以磁振照影探討入睡歷程意識轉變之神經生理基礎

Abstract

意識為一基本的心理歷程，為個體眾多面向的內在經驗歷程之整合，然而受限於其 核心為主觀的經驗與知覺，需要個體的自陳經驗報告，其基本機制的了解仍相當有限， 近年來運用功能性影像造影技術對於意識的神經生理基礎開始有初步的了解。政大睡眠 研究室之前的研究發現入睡階段是個伴隨對外界知覺以及內在思考逐漸下降的歷程，此 一歷程提供了一個機會可以檢視意識經驗與腦部活化狀態的關聯性。因此，本研究的目 的在於利用磁振造影技術與主觀意識經驗的測量來探討入睡過程中意識轉變的神經生 理基礎。本研究擬招募 20名健康受試者，請他們在實驗室嘗試入睡，並同時進行 EEG 與 fMRI的記錄，在特定 EEG定義的入睡狀態當中喚醒受試者，詢問其喚醒前的主觀意 識程度、睡眠知覺、以及感官知覺、思考內容及歷程、情緒經驗、定向感及現實感等主 觀經驗向度，分析喚起前腦部預設模式神經網路（DMN）、前額葉以及視丘皮質等意識 經驗相關腦部區域及神經迴路的功能性連結與活化程度，並以迴歸分析找出能預測主觀 意識狀態的腦部迴路。預期研究結果為 DMN、前額葉及視丘皮質等腦部區域預測主觀 意識狀態的程度應有所不同，有助澄清主觀意識經驗是否為一「整體狀態」，存在一核 心區域來控制，或由不同向度經驗的整合結果，進一步對意識現象的本質及相關神經機 制有更多的釐清及瞭解。

Consciousness is a basic mental process, a state of being aware of an external stimulus or an internal process. Because subjective reports are essential to any investigation of consciousness, scientific studies of and the understanding of its basic mechanism are limited. Recently, however, advances in brain imaging technics have enhanced our ability to probe, and thereby understand, the neural substrates of consciousness. Previous studies conducted by our laboratory showed that the sleep onset period is characterized by a gradual decrease of perceptual experience, followed by alterations in and reductions of thought processes. These transitional stages provide an opportunity to study the association between conscious experiences and brain activities, viz. the neural correlates of those distinct conscious states that constitute the transition. Thus, the aim of the proposed study is to use fMRI and subjective interview to explore the neurophysiological basis of the transition in states of consciousness during the sleep onset process. The study will recruit 20 young, healthy adults as subjects. Simultaneous EEG and fMRI recordings will be conducted while they are trying to fall asleep. They will be awakened at particular intervals during the sleep onset process, intervals that will be determined by EEG signals. They will then be interviewed concerning the status of their subjective consciousness immediately prior to having been awakened—their perceptual experiences, thought content and processes, emotional experiences, engagement with reality, and orientation toward time and place. Their metabolism and functional connectivity within the default mode network (DMN), as well as the prefrontal cortex and the thalamo-cortical system will also be measured. Regression analysis will be performed to identify the neural network associated with subjective consciousness state. It is expected that the DMN, the prefrontal cortex and the thalamo-cortical networks will show different association with different consciousness experiences. The results will provide evidence to clarify if consciousness is associated with a particular network or be the results of multiple networks associated with different aspects of subjective experiences. It will further our understanding of the neural substrates of consciousness as well as of the transition between waking and sleep states.