Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond St, London, Ontario, N6A 3K7, Canada.; Department of Physics, Faculty of Applied Sciences, University of Sri Jayewardenepura, Nugegoda, Sri Lanka; Brain and Mind Institute, University of Western Ontario, 1151 Richmond St, London, Ontario, N6A 3K7, Canada.
Institute of Biotechnology, Universidad Nacional de Colombia, Cra 45, Bogotá, Colombia.
Neuroimage. 2020 Dec;223:117367. doi: 10.1016/j.neuroimage.2020.117367. Epub 2020 Sep 12.
Propofol is a short-acting medication that results in decreased levels of consciousness and is used for general anesthesia. Although it is the most commonly used anesthetic in the world, much remains unknown about the mechanisms by which it induces a loss of consciousness. Characterizing anesthesia-induced alterations to brain network activity might provide a powerful framework for understanding the neural mechanisms of unconsciousness. The aim of this work was to model brain activity in healthy brains during various stages of consciousness, as induced by propofol, in the auditory paradigm. We used the generalized Ising model (GIM) to fit the empirical fMRI data of healthy subjects while they listened to an audio clip from a movie. The external stimulus (audio clip) is believed to be at least partially driving a synchronization process of the brain activity and provides a similar conscious experience in different subjects. In order to observe the common synchronization among the subjects, a novel technique called the inter subject correlation (ISC) was implemented. We showed that the GIM-modified to incorporate the naturalistic external field-was able to fit the empirical task fMRI data in the awake state, in mild sedation, in deep sedation, and in recovery, at a temperature T* which is well above the critical temperature. To our knowledge this is the first study that captures human brain activity in response to real-life external stimuli at different levels of conscious awareness using mathematical modeling. This study might be helpful in the future to assess the level of consciousness of patients with disorders of consciousness and help in regaining their consciousness.
异丙酚是一种短效药物，会导致意识水平下降，用于全身麻醉。尽管它是世界上最常用的麻醉剂，但对于它诱导意识丧失的机制仍有很多未知。描述麻醉诱导的大脑网络活动改变可能为理解无意识的神经机制提供一个强大的框架。这项工作的目的是在听觉范式中，使用广义伊辛模型 (GIM) 对健康大脑在异丙酚诱导的不同意识状态下的大脑活动进行建模。我们使用 GIM 拟合健康受试者听电影音频片段时的 fMRI 数据。外部刺激（音频片段）被认为至少部分驱动大脑活动的同步过程，并为不同的受试者提供类似的意识体验。为了观察受试者之间的共同同步，我们实施了一种称为主体间相关性（ISC）的新技术。我们表明，经过修改以纳入自然外部场的 GIM 能够拟合清醒状态、轻度镇静、深度镇静和恢复状态下的经验性任务 fMRI 数据，在温度 T* 下，远高于临界温度。据我们所知，这是第一项使用数学模型捕获人类大脑对不同意识水平的真实外部刺激的反应的研究。这项研究将来可能有助于评估意识障碍患者的意识水平，并帮助恢复他们的意识。
