FIG. 4.

Vestibular perceptual thresholds (a yaw rotation, b y-translation, and c roll tilt) measured for the same ten subjects in two conditions: with placebo and with promethazine. Gray lines represent individual subjects, and black lines represent the average, calculated as geometric mean, and standard deviation of the thresholds across subjects. Threshold data are presented using a logarithmic scale. There was a statistically significant change of +31 % in roll tilt thresholds (see c) after the intake of 25 mg of promethazine. Yaw rotation and y-translation thresholds showed an increase of +10 and +18 % with promethazine, although these changes were not statistically significant. d–f % Change in thresholds due to promethazine relative to placebo for each of the subjects (subjects are presented in the same order in each of the three panels).