Delay of simple reaction time after levodopa intake

Background: Parkinsonian patients (PP) have deficits in the preparation and execution of movements. It is generally accepted that PP show delayed performance of simple reaction time (SRT) paradigms due to impaired response preprogramming. To date, no trial considered putative effects of dopaminergic substitution on SRT performance in PP. Objectives: To determine short-term effects of acute levodopa intake and impact of long-term dopaminergic substitution on the results of a SRT task. Methods: We repeatedly performed a SRT paradigm in previously untreated- and treated PP, taken off medication for at least 12 h, before and after intake of levodopa/benserazide and in PP, who received placebo. Results: Reaction time significantly increased and movement time did not change after levodopa intake. Placebo application showed no effects. Conclusions: Levodopa delayed cognitive processing and/or behaviour. Sedative effects of levodopa and/or dopamine overflow in prefrontal regions with subsequent cholinergic dysfunction hypothetically caused this phenomenon