The detection of anisochrony in monaural and interaural sound sequences.

Nakao and Axelrod (1976) and van Noorden (1975) showed that the threshold for discriminating an anisochronous duple rhythm (a series of clicks with a temporal offset on every other one) from an isochronous rhythm (no offset) is poorer when the clicks are presented alternately to the two ears than when they are presented to the same ears. Van Noorden reported that the difference between the thresholds in the alternating and nonalternating conditions varied with the tempo of the sequence. Nakao and Axelrod found invariance of this threshold difference with sequence speed. According to our quantification of temporal processing of interaural sequences, the latter result should be expected. We carried out five psychophysical experiments to establish interaural and monaural discrimination between isochronous and anisochronous rhythms. Across experiments, base time intervals of 60-720 msec were spanned. The main result was that we replicated the poorer discrimination for interaural sequences. This deterioration in discrimination was the same for all sequence speeds. It was also the case that the thresholds were almost constant up to a sound repetition rate of about 3 per second, but increased linearly with slower rates. This result supports evidence in the literature that temporal processing of sequences faster than about 3-4 sounds per second differs from temporal processing of slower sequences.

The influence of antihistamines on human performance.

We have studied the effects of three antihistamines on task performance in two separate experiments. Healthy subjects were tested at weekly intervals in a double-blind, Latin square design. In Experiment I the subjects were treated orally with loratadine 10 mg, clemastine 1 mg, terfenadine 60 mg, or placebo. In Experiment II 5 mg diazepam was given orally with each of the four treatments used in Experiment I. In both experiments subjects' performance was evaluated in reaction time and tracking tasks after treatment. In both experiments, the tracking task initially was performed alone and then simultaneously with a continuous memory task; the subject also graded their mental status on visual analogue rating scales. In both experiments task performance was not generally impaired after treatment with loratadine or terfenadine. The concomitant administration of diazepam in Experiment II appeared not to affect subjects' performance. However, clemastine caused a decay in subjects' performance in both Experiments I and II, but only on the tracking task. At the conclusion of both experiments, sleepiness was reported by more subjects when treated with clemastine than when treated with loratadine, terfenadine, or placebo.