Objective: The aim of this study is to test motor decision-making ability in Parkinson’s disease (PD) in conditions with different biomechanical properties and levels of automatism.

Background: Volitional motor control usually involves deciding ‘where to go’ and ‘how to go there’, process known as implicit motor decision-making. The dopaminergic nigro-striatal pathway is crucial in the evaluation of rewards associated with movements, thus making it a possible candidate for motor decision-making. PD is a neurodegenerative disorder, whose pathological hallmark is the degeneration of dopaminergic neurons in the substantia nigra pars compacta.

Method: Fifteen PD patients and thirteen age-matched controls (CG) performed the “manifold reaching paradigm” (Berret et al., 2011), consisting in pointing movements towards a horizontal bar where the endpoint was not defined. Movements were executed with the right upper-limb starting from two positions, which were in the same (right) or in contralateral (left) hemi-space. Spatial pointing parameters and movements’ temporal features were evaluated.

Results: Starting from right position, PD movements were characterized by greater trajectory length and variability, and pointing variability than CG movements. In that position, the time devoted to decelerate was shorter in PD than in CG. No differences between groups appeared for movements starting from the left position. Finally, only for movements starting from  the right position, a significant negative correlation emerged between the variability of the trajectory length and the disease duration.

Conclusion: Altered motor-decision making in PD when dealing with more complex, although more automatic, movements can explain these results, suggesting a crucial role of the fronto-striatal loop in motor decision-making process.

References: B. Berret, E. Chiovetto, F. Nori, T. Pozzo, Manifold reaching paradigm: How do we handle target redundancy? J. Neurophysiol. 106, 2086–2102 (2011).

« Back to 2022 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/motor-decision-making-in-parkinsons-disease/