The influence of Parkinson's disease on the functional connectivity of the motor loop of human basal ganglia

Current basal ganglia models integrate information obtained from humans and animals to explain motor disorders in Parkinson's disease. These models explain some motor disturbances of Parkinson's disease (PD), but different clinical observations which remain unexplained have promoted the development of new basal ganglia (BG) models. The present study uses the time-relationship (partial correlation) of the BOLD-signal fluctuations to study the influence of PD on BG interactions of 17 age-matched controls (58.7 +/- 5.3 years of age) and 24 PD patients (56.7 +/- 8.4 years of age). Controls showed a complex functional connectivity of BG with a positive correlation between some nuclei (synchrony) and a negative correlation between other nuclei (anti-synchrony). This functional connectivity was different in PD-patients who showed: 1. an increased synchrony between the primary motor cortex(M1)-external pallidum(GPe), putamen(Put)-GPe, Put-subthalamic nucleus (STN), STN-internal pallidum (GPi), STN-motor thalamus (Tal), STN-GPi substantia nigra (SN) and SN-Tal, 2. a decreased synchrony between Put-GPi, GPe-STN, GPe-SN, STN-SN and GPi-SN, and 3. an increased anti-synchrony between GPe-SN and GPi-Tal. In control subjects, the motor-task increased the Put-Tal, GPi-SN and STN-Tal synchrony, decreased the STN-GPi and STN-SN synchrony and decreased the M1-GPe and the GPe-GPi anti-synchrony. The effect of the motor-task was very different in PD-patients, in whom it induced a decrease of the M1-GPe, STN-GPi and SN-Tal synchrony and a decrease of the GPe-Tal and GPe-SN anti-synchrony. Functional connectivity imaging methods may provide data that cannot be obtained by other methods in humans, and that may help to understand the physiology of BG and its deterioration in PD.