Functional and structural connectivity in the motor system in healthy people and in patients with Parkinson’s disease

Parkinson’s disease is the second most frequent chronic neurodegenerative disorder affecting up to 2% of individuals aged 65 years and older. This pathology affects the motor processes determining the patients to have significant difficulties in daily chores. We analysed the influence of transcranial magnetic stimulation on the reaction time in 14 patients with Parkinson’s disease and 13 healthy controls. In a second study we measured the cortical thickness, cortical area and the volumes of thalamus, caudate nucleus, putamen and pallidum of 84 patients and 43 healthy controls. Our results revealed a slower reaction time in patients with Parkinson’s disease when compared to healthy controls. The reaction time was quicker in both groups after applying the magnetic stimulation pulse but patients with Parkinson’s disease still had a slower reaction time compared to healthy controls. Reaction time parameters correlated with a higher cortical thickness in the cingulate motor region and with a lower cortical thickness in the temporal and parietal regions. The second study showed decreased cortical thickness and surface area in Parkinson’s disease patients in the primary motor area, ventral premotor area and the supplementary motor cortex. Decreased cortical area in the motor regions correlated positively with the volumes of the caudate nucleus, putamen and pallidum. The present study shows a different pattern of functional and structural interactions in the motor regions in patients with Parkinson’s disease. Specifically functional and structural connectivity changes due to impaired reaction time were detected in the cingulate motor area, ventral premotor and supplementary motor areas Furthermore, cortical remodelling in PD are associated with changes in the volumes of the caudate nucleus, putamen and pallidum. Both degeneration processes as well as compensatory mechanisms of the brain can explain these changes.