Abstract
The effect of pentymal, diazepam (Valium) and placebo on motor reaction time, (RT), threshold latency and rise time of the stapedius reflex has been studied in 18 normal hearing subjects. The results are presented in two ways. First the effects of the soporific and tranquilizer were compared with the normal values for RT, threshold, latency and rise time based on 2160 measurements. In all of ten different conditions Pentymal caused significant longer RT, in nine often conditions diazepam gave similar effect. Placebo resulted in prolonged RT in five of ten conditions. No significant effect could be demonstrated on the stapedius reflex. In the second part of the investigation the group difference between the measurements before and after drug ingestion was examined at every test session. The statistical tests have been carried out, based on paired comparisons for each subject under each drug condition. In only five of ten different conditions in this comparison did Pentymal give significant prolonged RT. Diazepam gave corresponding results in only four of ten conditions and placebo did not change RT. Nor was the stapedius reflex influenced. We conclude that both Pentymal and diazepam impair motor performance in some individuals and that the effect is variable and not obviously predictable. The stapedius reflex measure, on the other hand, appears insufficiently sensitive to evaluate the effects of these drugs in man.