Objective:
The aim of this study was to investigate whether impaired execution of drawing spirals relates to deteriorations in interregional connectivity.

Background: Movement execution is impaired in patients with Parkinson’s disease (PD). Evolving neurodegeneration leads to altered connectivity between distinct regions of the brain and altered activity at interconnected areas. How connectivity alterations influence complex movements like drawing spirals in PD patients remains largely unexplored.

Method: 29 Patients (age: 62.45 ± 10.09 years; Hoehn and Yahr: 2.66 ± 0.97) and 31 age-matched healthy control participants (age: 64.72 ± 7.51) drew spirals with both hands on a digital graphics tablet, and the regularity of drawing execution was evaluated by sample entropy. We recorded resting-state fMRI and task-related EEG, and calculated the time-resolved partial directed coherence to estimate effective connectivity for both imaging modalities to determine the extent and directionality of interregional interactions.

Results: Movement performance in PD patients was characterised by significantly increased sample entropy, corresponding to enhanced irregularities in task execution. Therefore, non-linear parameters like sample entropy have the potential to detect aberrant characteristics of graphomotor performance in medicated PD patients. Effective connectivity between the motor cortices of both hemispheres, derived from resting-state fMRI, was significantly reduced in PD patients in comparison to controls. The connectivity strength in the non-dominant to dominant hemisphere direction in both modalities was inversely correlated with irregularities during drawing.

Conclusion: Our findings suggest that interhemispheric connections between the two hemispheres are affected both at rest and during drawing movements by PD. Linear correlations between connectivity parameters captured by both resting-state fMRI and task EEG with graphomotor performance highlight that intact information exchange from the non-dominant to dominant motor cortex seems related to fine motor control in patients with PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/deficient-interhemispheric-connectivity-underlies-movement-irregularities-in-parkinsons-disease/