| || |
|Title:||MOVEMENT CHUNKING IN PARKINSON ’S DISEASE IS DOPAMINEDEPENDENT|
| || |
|Authors/Affiliations:||2 Pierre-Luc Gilbert Tremblay*; 2 Dominic Langlois; 2 Marc-André Bédard; 1 Blanchet Pierre J; |
1 CHUM and Université de Montréal; 2 UQAM; Montreal, QC, Canada
| || |
|Content:||OBJECTIVE: Chunking of single movements into integrated sequences has been described during motor learning. Dopamine D2-receptor blockade and MPTP-induced lesioning of the nigrostriatal dopamine system have been shown to disrupt this chunking process. However, there is no evidence of such a dopaminedependent chunking process in humans.The current study aimed at better defining the role of dopamine in the movement chunking process in Parkinson’s disease (PD). |
MATERIALS AND METHODS: Eleven mild to moderate PD patients were seen twice, under their usual levodopa dopaminergic medication (ON state), and following a 12hour levodopa withdrawal (OFF state). The ON-OFF conditions were counterbalanced, and always occurred within a 24hour delay. Patients were compared with 12 healthy subjects on a motor learning sequencing task, requiring to successively press seven pairs of buttons. This task was performed for three consecutive blocks of 20 trials, allowing to progressively observe movement chunks along trials. Total learning was measured by the total execution time for a sequence and chunking was mesured using ETA-squared ( 2 ), a quantitative evaluation of the variance explained by the independent variable. Then, a new motor sequence either made out of the specific participant’s chunks (Preserved chunks condition), or made out of artificially created chunks (Broken chunks condition), was learned by the participants.
RESULTS: Results showed no difference in the learning profile between the ON and OFF conditions, nor between normal controls and PD patients. However, total learning in PD patients was significantly higher in the ON than in the OFF condition. Chunking during motor learning was similar between control subjects and ON but not OFF PD patients. Chunking was also poorer in the OFF than in the ON condition. Moreover, in the Preserved chunks condition chunking was significantly better in normal subjects and in ON PD patients, than in OFF PD patients. Comparisons between the Preserved and the Broken chunks conditions on the learning score revealed significant differences in both control subjects and ON PD patients, but not OFF PD patients.
CONCLUSIONS: These results suggest a greater ability to learn sequences made of the chunks previously learned when dopamine is present. It also suggests that chunking during motor learning is a dopaminedependent process.
| || |