Parkinson’s disease is traditionally described as a movement disorder, characterized by tremor, muscle rigidity, slowed movements, and impaired balance. However, many individuals with Parkinson’s also experience prominent non-motor symptoms, including sleep disturbances, anxiety, depression, reduced motivation, and difficulties with thinking. A large new study proposes that this wide range of symptoms may arise from dysfunction within a single brain network that integrates movement, bodily regulation, and cognition.
The researchers analyzed brain imaging and treatment outcomes of 863 individuals, comprising people with Parkinson’s disease and healthy control subjects. Their discussion focused on a newly discovered brain structure called the somato-cognitive action network (SCAN). This network helps coordinate whole-body activities, motivation, arousal, and autonomic processes like heart rate and digestion. Unlike traditional motor regions, which control specific body parts (e.g., hand or foot), the SCAN operates at a broad, integrated, whole-body level.
Using resting-state functional MRI, the researchers found that several deep brain structures implicated in Parkinson’s disease, including the substantia nigra, subthalamic nucleus, globus pallidus, thalamus, and putamen, were more strongly connected to the SCAN than to motor regions representing specific body parts.
Notably, an excessively close connection was observed between these subcortical regions and the SCAN in patients with Parkinson’s. This pattern of hyperconnectivity was distinct from that observed in healthy individuals or in other movement disorders, including essential tremor, dystonia, or amyotrophic lateral sclerosis. The level of such abnormal connectivity was associated with clinical symptoms.
Higher levels of SCAN hyperconnectivity were associated with impaired motor function (measured by the MDS-UPDRS-III), lower cognitive performance (Mini-Mental State Examination), and increased anxiety and depression. These findings support the notion that SCAN dysfunction contributes to both motor and non-motor symptoms of Parkinson’s disease.
This study also addressed the effect of the various treatments on SCAN connectivity. Patients receiving levodopa, deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), or MRI-guided focused ultrasound (MRgFUS) were monitored. Effective treatment consistently suppressed SCAN hyperconnectivity. In DBS patients, changes in SCAN connectivity paralleled improvements in motor symptoms, gradually normalizing toward levels observed in healthy participants.
Regarding non-invasive brain stimulation, a randomized trial of 36 patients demonstrated that TMS targeting the SCAN produced about twice the improvement in motor symptoms compared with TMS applied to the traditional motor areas. Rapid improvement of patients undergoing SCAN-targeted stimulation was also observed, particularly regarding bradykinesia, rigidity, tremor, and axial symptoms. Similarly, patients who underwent focused ultrasound treatment showed better outcomes when the lesion was placed closer to the thalamic SCAN “sweet spot.”
Taken together, these findings suggest that Parkinson’s disease may be better understood as a disorder of the somato-cognitive action network, rather than a condition confined solely to traditional movement pathways.
The researchers propose that SCAN hyperconnectivity may be used as a non-invasive biomarker for Parkinson’s disease and guide more precise treatment strategies. This network-based approach has the potential to inform safer and more effective treatment options that target the fundamental brain networks underlying both motor and non-motor symptoms.
Reference: Ren J, Zhang W, Dahmani L, et al. Parkinson’s disease as a somato-cognitive action network disorder. Nature. 2026. doi:10.1038/s41586-025-10059-1
