Abstract
Unlike processing of time intervals in the range of seconds or more, processing of brief durations ranging from approximately 50 to 100 ms appears to be beyond cognitive control and based on neural counting mechanisms. In a placeboβcontrolled study either 15 mg of midazolam or placebo were applied to 36 healthy male volunteers to investigate the effect of pharmacologically induced sedation on temporal processing of intervals in the range of milliseconds indicating performance on time perception and in the range of seconds indicating performance on time estimation. In addition, a test battery consisting of subtests measuring speed of information processing and cortical arousal was applied. Midazolam induced a very pronounced decrease in cortical arousal as well as a marked impairment of speed of information processing and performance on time estimation as compared to placebo. Performance on time perception, however, was not affected suggesting that temporal processing of very brief intervals is unrelated to the effective level of cortical arousal. These findings support the notion of two different timing mechanisms underlying time estimation and time perception.