Novel Brain Network Implicated in Parkinson's Disease: The Somato-Cognitive Action Network (SCAN)
An international research effort has identified the somato-cognitive action network (SCAN) as a key brain network implicated in Parkinson's disease (PD). The study, which analyzed brain imaging data from over 800 participants, found abnormal hyperconnectivity within SCAN in individuals with Parkinson's. The findings suggest that effective treatments for PD function by reducing this hyperconnectivity. Researchers also developed a non-invasive precision treatment using transcranial magnetic stimulation (TMS) targeting the SCAN, which demonstrated a higher response rate in a preliminary clinical trial.
Understanding Parkinson's Disease
Parkinson's disease is a neurological disorder affecting over 10 million individuals globally. It is characterized by a range of symptoms, including tremors, difficulties with movement, sleep disturbances, and cognitive impairments. Non-motor symptoms such as issues with smell, digestion (including chronic constipation), memory lapses, and fatigue are also common. Historically viewed primarily as a movement disorder, Parkinson's is increasingly understood as a network disorder involving multiple brain systems, explaining the diverse symptoms experienced by patients. Current treatments primarily manage symptoms without halting disease progression.
The Somato-Cognitive Action Network (SCAN) Identified
A study co-led by researchers from China's Changping Laboratory and Washington University School of Medicine in St. Louis identified the somato-cognitive action network (SCAN) as central to the core issues observed in Parkinson's disease. The SCAN, located within the motor cortex, plays a role in converting action plans into movements and processing feedback. This network connects various bodily and cognitive functions, including those responsible for involuntary processes like heart rate, digestion, and blood pressure, as well as functions related to REM sleep, memory, and thinking.
Researchers propose that Parkinson's disease is a SCAN disorder.
Study Methodology and Key Findings
The research team, led by Hesheng Liu and Nico U. Dosenbach, collected brain imaging data from over 800 participants. This cohort included individuals with Parkinson's disease, healthy controls, and patients with other movement disorders. Participants included those undergoing treatments such as deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), focused ultrasound stimulation, and medication.
Analysis of the data revealed that Parkinson's disease involves hyperconnectivity between the SCAN and the subcortex, a brain region involved in emotion, memory, and motor control. This increased connectivity was observed as abnormally strong connections between the SCAN network and brain regions affected by Parkinson's, which was described as impeding normal signal transmission. This finding broadens the understanding of Parkinson's beyond primarily motor deficits linked to the basal ganglia, indicating a wider network dysfunction.
Impact on Existing Treatments
The study also examined the impact of existing Parkinson's treatments on the SCAN network. All four therapies investigated—deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), focused ultrasound stimulation, and medication (such as levodopa)—demonstrated maximum effectiveness when they reduced the identified hyperconnectivity. This reduction in abnormal connectivity normalized activity within the action planning and coordination circuit, allowing brain signals to flow more effectively.
Non-Invasive Precision Treatment Developed
Leveraging these insights, the researchers developed a non-invasive precision treatment system using transcranial magnetic stimulation (TMS). This system was designed to target the SCAN with millimeter accuracy. In a clinical trial involving 18 patients, SCAN-targeted TMS resulted in a 56% response rate after two weeks. This was compared to a 22% response rate in a control group of 18 patients who received stimulation in adjacent brain areas, indicating a 2.5-fold increase in efficacy for the SCAN-targeted approach. Non-invasive treatments like TMS offer potential for earlier intervention compared to surgical procedures such as DBS.
Future Outlook
Ongoing research aims to further elucidate how different components of the SCAN influence various Parkinson's symptoms. Plans include additional clinical trials to test non-invasive treatments, such as surface electrode strips and low-intensity focused ultrasound, specifically for gait dysfunction in Parkinson's patients. The precise, personalized targeting of the SCAN network has the potential to lead to more effective treatment outcomes and potentially slow or reverse disease progression, rather than merely addressing symptoms. Future therapies could target specific areas within the SCAN network to improve a broader spectrum of both motor and non-motor symptoms.