Parkinson’s disease causes the patient to lose motor control. The subject stiffens, tremors, and loses co-ordination. They are treated with DBS -deep brain stimulation, targeting the subthalamic nucleus (STN). This therapy’s neuromodulatory effects on the whole brain are still elusive. The technical deficiency highlights a distinct lack of understanding of large-scale brain networks. This study investigates DBS-STN in patients with PD.

The study aims to find whole-brain effects using 3T-MRI stimulator. A group of 14 patients participated in the experiment. A block design delivered interleaved ON and OFF stimulations. The fMRI responses to low and high frequency, 60 Hz to 130 Hz were measured. They were recorded 1, 3, 6, and 12 months after surgery. Multiple runs for 48 minutes on each visit ensured reliable fMRI data. Pre-surgical fMRI data for 30 minutes were also collected.

Two neurocircuits showed responses to STN-DBS. The globus pallidus internus, thalamus, and deep cerebellar nuclei were activated. Whereas, the deactivation was found in the primary motor cortex, putamen, and cerebellum. The two circuits could be disassociated based on induced responses and resting-state functional connectivity. The GPI circuit selectively responded to high frequency. It was associated with overall motor improvements. And, the M1 circuit gradually deactivated over time. Its reduction is linked to lowering bradykinesia.

Two distinct circuits with diverging symptoms were located. They may provide new insights into underlying neural mechanisms.