Parkinson's disease (PD) patients may experience fluctuations in executive performance after oral levodopa (LD). Their relationship with the pharmacokinetic profile of LD and with distinct cognitive processes associated with frontal-basal ganglia circuits is not well understood. In this randomized, double-blind, crossover study we plotted acute cognitive changes in 14 PD patients challenged with faster (immediate-release, IR) versus slower (controlled-release, CR) increases in LD plasma concentrations. We monitored motor status, LD plasma levels, and performance on four tasks of executive function (Wisconsin Card Sorting Test - WCST, Sternberg test, Stroop and Tower of Hanoi), 1 hr before and over +6 hr after IR and CR-LD dose. Analysis of variance demonstrated significant but divergent changes in the Sternberg (6-digit but not 2- and 4-digit) test: improvement after CR-LD and worsening after IR-LD. Marginal improvement (p = .085) was observed with CR-LD in the WCST, while no significant differences were seen for the Stroop or Tower of Hanoi tests. Executive-related performance after LD challenge may differ depending on the LD time-to-peak plasma concentration and specific task demands. A slower rise in LD levels appears to have a more favorable impact on more difficult working memory tests. These results require replication to determine their generalization. © 2008 INS.
|Journal||Journal of the International Neuropsychological Society|
|Publication status||Published - 15 Sep 2008|
- Basal ganglia
- Frontal lobe
- Neuropsychological tests