Fig. 2. rCBF values in right and left regions of interest (ROIs) are plotted by drug concentration and auditory word rate condition. rCBF values are normalized during SPM analysis so that global blood flow across all conditions and drug concentrations is 50 ml·100−1g brain tissue·min−1. This accounts for differing values in this figure from figures 3 and 4. A monotonically increasing rCBF response with auditory stimulus rate is present in all ROIs at baseline and during sedation. This relationship is absent during unresponsiveness for 10 participants as a group, but there is a diminished response present in seven of 10 participants (square symbols) on the L side. These seven participants have the same rCBF response as the group as a whole during baseline and sedation conditions. Heschl’s gyri demonstrate similar rCBF responses to word rate. Higher rCBF values are likely attributable to the fact that less white matter is included in the Heschl’s ROI than in the spherical ROIs (spherical regions of interest are not completely spherical, as any regions outside the brain have been excluded). B = baseline, S = sedation, H = hypnotic drug concentrations. Word rates are 0, 20, or 40 words per minute. Error bars represent SD.