Objective: To study network interactions of patients with Parkinson’s disease (PD) and healthy controls (CT) during handwriting with and without external visual cues and to investigate the effect of long-term visually-cued writing training on network interactions in PD.

Background: A common motor symptom of PD is micrographia, characterized by a decrease in writing amplitude. Despite the relevance of this impairment, the underlying neural network abnormalities and the impact of training interventions on brain connectivity are mostly unknown.

Methods: We analyzed fMRI-data using dynamic causal modeling to investigate neural network dynamics of amplitude training for micrographia compared to placebo training. We also examined the effects of visual cues. At baseline, 28 patients with early PD on dopaminergic medication and 14 age-matched CTs performed a pre-writing task in the presence and absence of visual cues in the scanner. Subsequently, patients were randomized to an experimental writing training and a placebo intervention of six weeks, after which they underwent the same scanning procedure.

Results: At baseline, patients displayed weaker right visuo-parietal coupling during writing, suggesting that impaired right hemispheric visuomotor integration may contribute to micrographia. During cued writing both groups displayed stronger excitatory coupling onto the left superior parietal lobe from visual and premotor areas, largely consistent with previously identified ‘external’ motor control pathways. In the absence of cues, there was stronger coupling in the motor control network, with increased parieto-premotor, premotor-cerebellum and premotor-M1 connectivity. The most important results pertained to the impact of training. We found that intensive writing training propagated connectivity via the left hemispheric visuomotor stream to an increased coupling with the supplementary motor area. This pattern was not apparent in the placebo group.  Interestingly, training did not lead to normalization of network interactions.

Conclusions: Our findings imply that training effects rely on the functional reserve of brain networks, which remain relatively unaffected by the disease. We conclude that in early PD experience-dependent brain reorganization remains possible in cortical networks after prolonged training and induce clinical improvement in concert with dopaminergic treatment.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/writing-training-enhances-neural-connectivity-in-parkinsons-patients-with-micrographia/