Changes in Effective Connectivity by Propofol Sedation

Mechanisms of propofol-induced loss of consciousness remain poorly understood. Recent fMRI studies have shown decreases in functional connectivity during unconsciousness induced by this anesthetic agent. Functional connectivity does not provide information of directional changes in the dynamics observed during unconsciousness. The aim of the present study was to investigate, in healthy humans during an auditory task, the changes in effective connectivity resulting from propofol induced loss of consciousness. We used Dynamic Causal Modeling for fMRI (fMRI-DCM) to assess how causal connectivity is influenced by the anesthetic agent in the auditory system. Our results suggest that the dynamic observed in the auditory system during unconsciousness induced by propofol, can result in a mixture of two effects: a local inhibitory connectivity increase and a decrease in the effective connectivity in sensory cortices.丙泊酚诱导意识丧失的具体机制迄今仍未被充分阐明。近期的功能磁共振成像（functional magnetic resonance imaging，fMRI）研究显示，在该麻醉剂诱导的意识丧失状态下，脑功能连接会出现减弱现象。但功能连接无法反映意识丧失过程中观测到的神经动力学的方向性变化。本研究旨在针对健康受试者开展听觉任务，探究丙泊酚诱导意识丧失所引发的有效连接变化。我们采用针对功能磁共振成像的动态因果建模（fMRI-DCM），评估该麻醉剂对听觉系统内因果连接的影响。本研究结果表明，丙泊酚诱导意识丧失时听觉系统观测到的神经动力学，可由两种效应共同介导：局部抑制性连接增强，以及感觉皮层的有效连接减弱。