ON DOPAMINERGIC MODULATION OF TEMPORAL INFORMATION-PROCESSING

Temporal processing of durations in the range of seconds or more (i.e. time estimation) is cognitively mediated, whereas processing of brief durations in the range of milliseconds (i.e. time perception) appears to be beyond cognitive control and based on neural counting mechanisms. Although there is some evidence from animal and human studies suggesting that the internal timing mechanism underlying time perception is modulated by the effective level of brain dopamine, the findings are not conclusive. Therefore, the effects of pharmacologically induced changes in D2 receptor activity on temporal information processing were evaluated. In a double-blind design, either 3 mg of haloperidol, 150 mg of remoxipride, or placebo were administered in a single oral dose. Performance on time estimation was significantly impaired by both haioperidol and remoxipride as compared with placebo. Both drugs obviously affected cognitive mechanisms underlying temporal processing of durations in the range of seconds. On the other hand, only haloperidol produced a significant decrease in performance on time perception as compared with placebo and remoxipride, whereas the remoxipride and placebo groups did not differ significantly. The differential effects of haloperidol and remoxipride on performance on time perception suggest that D2 receptor activity in the basal ganglia may play a critical role in timing of brief durations in the range of milliseconds.