Deep brain stimulation modulates the dynamics of resting-state networks in patients with Parkinson's Disease

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is increasingly used for the treatment of Parkinsons Disease (PD), but despite its success, the neural mechanisms behind this surgical procedure remain partly unclear. As one working hypothesis, it was proposed that DBS works by restoring the balance of the brains resting-state networks (RSNs), which is reported to be disrupted in people with PD. Hence, to elucidate the effects that STN-DBS induces on disseminated networks, we analyzed an fMRI dataset of 20 PD patients at rest under DBS ON and OFF conditions. Moving beyond static functional connectivity studies, we employ a recently developed fMRI analysis tool, the Leading Eigenvector Dynamic Analysis (LEiDA), to characterize the recurrence of brain-wide phase-locking patterns overlapping with known RSNs. Here, STN-DBS seems to increase the Default Mode Network (DMN) occurrence in individuals with PD. Since the DMN is usually disturbed in PD patients presenting deficits in cognition, our observation might be suggestive that STN-DBS contributes to a normalization of the PD-induced cognitive impairment. Moreover, we addressed the effects of DBS lead placement on RSNs balance, considering the overlap between the DBS-induced electric field and 3 STN subsections. We found that the Visual Network (VN) probability of occurrence increased proportionally to the electric field-limbic STN overlap. Our finding might be indicative that stimulation of the limbic STN is related to the stabilization of visual symptoms sometimes presented by PD patients, which are usually accompanied by VN disruption. Overall, this study offers new insights into the fine-grained temporal dynamics of brain states portraying the effects of STN-DBS in patients with PD, while at the same time trying to pave the way to improved planning strategies for this surgical procedure.