Functional connectivity of brain areas fluctuates over time, even during anesthesia. By applying point process analysis to resting-state fMRI data from 18 healthy subjects during propofol-induced wakefulness, sedation, unconsciousness, and recovery, the study identified eight distinct co-activation patterns centered on the posterior cingulate cortex (PCC). The core of these patterns remained stable across consciousness levels, but propofol caused region-specific reductions in co-activation, including disconnections of the prefrontal cortex, thalamus, auditory cortex, motor cortex, and visual area. The methodology helps refine characterization of local functional brain changes associated with propofol-induced modulation of consciousness.
Propofol, the most common general anesthetic, induces loss of consciousness through mechanisms that remain poorly understood. Using the generalized Ising model (GIM) to analyze fMRI data from healthy subjects listening to an audio clip, brain activity was modeled during wakefulness, mild sedation, deep sedation, and recovery. A novel inter-subject correlation technique captured common synchronization across participants. The GIM, modified to incorporate the naturalistic external stimulus, successfully fitted empirical task fMRI data at a temperature well above the critical temperature. This is the first mathematical modeling of human brain activity responding to real-life stimuli at different conscious levels, potentially aiding assessment of consciousness in patients with disorders of consciousness.