Figure 1

Experimental design and regions of interest (ROIs). (a) Schematic of experimental set-up with stepwise intravenous infusion of propofol and fMRI tasks. The infusion rate was controlled to achieve propofol effect-site concentrations (E.S.C.) of 0, 0.4, 0.8, 1.2, 1.6, 2.0, and 2.4 μg/ml and each level was maintained for 5 minutes. Emergence from sedation began at the end of the 2.4 μg/ml test period by stopping the infusion. Mental imagery and motor response tasks were tested before, during and after propofol infusion. Subjects were asked to perform three imagery tasks (tennis, navigation and hand squeeze) plus a motor response task (actual hand squeeze). The timing of “action” instructions (expected motor response) and the actual motor response (P04 as an example) were used to determine the periods of responsiveness (PreLOR), loss of responsiveness (LOR), and recovery of responsiveness (ROR). Two 10-min resting-state fMRI, and two 15-min task fMRI (baseline) were studied before (Base1) and after (Base2) propofol infusion. (b) Probability maps of active regions across 5 subjects. The ROIs were individually defined for each condition by the overlapped activation maps across the four sessions, Base1, PreLOR, ROR and Base2. The ROIs included the supplementary motor area (SMA), premotor cortex (PreM), and precuneus/inferior parietal lobule (PreCu/IPL) for tennis imagery; the parahippocampal place area (PPA) and posterior parietal lobe (PPC) for navigation imagery; the SMA and PreM for squeeze imagery; and the primary motor cortex (M1) for actual motor response.