Objective: To investigate differences in the functional connectivity of motor regions between individuals with and without Parkinson’s disease (PD) during a force task requiring coordination between the hand and foot

Background: In a recent fMRI study by Chung and colleagues (2023)[1], we demonstrated that during an ipsilateral interlimb coordination force control task PD had impaired force control, decreased activity in the contralateral external globus pallidus (GPe), and both the hand and foot areas of M1, and increased activity in premotor and prefrontal regions as compared to controls. To further elucidate motor-related deficits in PD, a functional connectivity analysis was undertaken, offering an additional dimension to our understanding of the neural mechanisms underlying impairments.

Method: Participants included 20 individuals with PD and 20 age- and sex-matched controls who completed an isometric force control task involving simultaneous rapid contractions of the ipsilateral hand and ankle at 15% MVC. Whole-brain voxel-wise analyses were conducted to compare the functional connectivity of the contralateral GPe, M1, and pre-SMA between groups.

Results: PD demonstrated reduced functional connectivity between the contralateral GPe and contralateral hand and foot M1 regions, SMA, and the ipsilateral putamen. Additionally, reduced connectivity was observed between the contralateral M1 and SMA, putamen, and fronto-parietal regions, and between the contralateral pre-SMA and middle cingulate gyrus, dorsal premotor cortex, and visuomotor areas. Greater connectivity was found in PD between the contralateral M1 and inferior/middle frontal gyrus as well as between the contralateral preSMA and several frontal and temporal regions.

Conclusion: PD exhibit decreased connectivity between basal ganglia and cortical motor regions, and increased connectivity between the latter and attention/planning regions. Collectively, results suggest that functional brain changes in PD extend beyond changes in motor-related activity. They also entail changes in the dynamic interactions among these regions, indicative of a broader restructuring of functional connectivity networks that may serve as a potential compensatory mechanism for the compromised function of the basal ganglia.

References: [1] Chung JW, Bower AE, Malik I, Martello JP, Knight CA, Jeka JJ, et al. fMRI changes during multi-limb movements in Parkinson’s disease. Front Hum Neurosci. 2023 Nov 9;17:1248636.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/functional-connectivity-changes-associated-with-interlimb-coordination-force-deficits-in-parkinsons-disease/