Response preparation in Parkinson's disease: Automatic vs. controlled processing

Using a finger cuing paradigm, we investigated response preparation in Parkinson's disease (PD). The central question was whether PD individuals are differentially affected by preparatory cues that specify a more automatic response set configuration (that induces within-hand preparation) as opposed to a more controlled one (that induces between-hands preparation). Reaction times (RTs) and error rates were measured in 20 non-demented individuals with PD and 20 healthy control participants with a long and short preparation interval (500 ms and 2000 ms). RT benefits and/or costs were measured for cues indicating a within- and between-hands motor preparatory set. Overall, RTs were significantly longer, and errors more frequent, for PD participants than for control participants. More importantly, in comparison with control subjects, PD individuals showed a significant deficit in between-hands preparation but not in within-hand preparation. Furthermore, longer preparation intervals slowed down cued RTs of the control participants, but not those of the PD individuals. Together, these findings suggest that whereas automatic response preparation processes are spared in PD, controlled response preparation processes operate at a slower rate and/or are delayed in time

Serotonergic mechanisms in Parkinson's Disease: Opposing results from preclinical and clinical data.

Parkinson's disease (PD) is a neuropsychiatric disease affecting approximately 1-2% of the general population. The classical triad of symptoms, tremor, rigidity, and bradykinesia is mainly caused by degeneration of dopaminergic neurons from the substantia nigra. However, other neurotransmitter systems also show signs of degeneration, among which the serotonergic system. The exact role of serotonin in PD remains unclear. We present here a review about functional serotonergic interventions and serotonergic imaging studies in PD, and will go into the importance of combining preclinical and clinical research data in order to gain more insight into the role of serotonin in PD. More specifically, the present review is aimed at bridging the gap between data from animal models of PD and data from human research