Fig. 1. rCBF response to increasing auditory word rate at different drug concentrations is represented by increasingly hot colors with increased significance. Regions of interest (ROI) are outlined in black. Heschl’s ROIs are located anterior to ROIs that demonstrate peak covariation with word rate across all drug concentrations (baseline, sedative, and hypnotic concentrations) and conditions (word rate 0, 20, or 40 words per minute). Regions of covariation represent increases in rCBF as word rate increases. Axial brain slices through auditory cortex are presented from z = 0 to z = 12 mm in the standard MNI brain atlas. Each row of images represents a different drug concentration starting from baseline at the top to hypnotic concentrations where participants are unresponsive. At the hypnotic drug concentration no covariation of rCBF with word rate was found among all 10 participants as a group. However, seven of 10 participants demonstrated a diminished rCBF response in comparison with baseline in the left ROI. The scale represents statistical significance, and only regions with significance of T>2.5 are shown. In terms of significance, a T value of 3.21 is the same as P < 0.001 SPMuncorrected, and a T value of 4.57 is the same as P < 0.05 SPMcorrected (across all voxels of the brain).