A study investigating the functional connectivity of the praxis network in patients in the early stages of Parkinson’s disease
(PD) found that dopaminergic therapy may normalize praxis abilities and related praxis networks during the early stages of the disease by facilitating the propagation of long-term representations of object-related actions to motor execution areas.
involved 13 patients with mild to moderate PD, including those ON or OFF dopaminergic therapy. These patients, as well as 13 healthy controls, completed a praxis sensitive functional MRI task and apraxia assessments. The results were analyzed with consideration for the global efficiency within the praxis network, followed by a seed-to-voxel functional connectivity analysis.
“Apraxia is a cognitive motor disorder affecting the performance of skilled and purposeful movements such as tool use or gesture production,” explained the authors. “Deficits in praxis functions can have obstructive effects on the activities of daily living and can significantly impair the patients' ability to live autonomously. Apraxia occurs in a variety of neurological diseases including stroke, dementia, and movement disorders.”
The analyses revealed that patients OFF dopaminergic therapy demonstrated significantly lower praxis scores than controls. However, patients in both the ON and OFF states displayed higher global efficiency within the praxis network than the controls—suggesting bilateral supramarginal gyri as hubs, according to the research. Patients in the ON stage were found to have significantly higher functional connectivity between supramarginal gyrus and the primary motor cortex, basal ganglia, and frontal areas, than the OFF state.
“Dopaminergic therapy induced an increased FC between the supramarginal gyrus and motor areas that might facilitate the propagation of long-term representations of object-related actions to motor execution areas,” concluded the authors. “Besides the well-known effects on basal motor functions dopaminergic therapy seems to support higher-order cognitive motor functions such as praxis abilities and related networks – at least in early stages of PD.”
The study recommended future studies with patients with PD be conducted with and without clinical apraxia in order to better understand the relation between functional connectivity, aberrant praxis related activation, and behavioral apraxic symptoms.
Matt E, Fischmeister F, Foki T, et al. Dopaminergic modulation of the praxis network in Parkinson's disease [published online August 18, 2019]. Neuroimage Clin