Parkinson's disease may no longer be considered solely a disorder of the basal ganglia. An international study, published in the journal Nature, highlights a specific brain network whose dysfunction appears to be at the heart of the disease: the somato-cognitive action network, or SCAN.
Led by the Changping laboratory in China in collaboration with Washington University in St. Louis, the research offers a new interpretation of the neurological mechanisms of Parkinson's, a condition that affects more than ten million people worldwide.
A network that links cognition and movement
The SCAN is located in the motor cortex, a region involved in the planning and execution of movements. It ensures the transformation of intentions into concrete actions and receives feedback on the quality of the execution.
However, according to researchers, Parkinson's disease is characterized by hyperconnectivity between this network and the subcortex, an area involved in emotions, memory, and motor control. This excessive connectivity disrupts not only movement but also certain cognitive and bodily functions, such as sleep and digestion.
To reach these conclusions, the team analyzed brain imaging data from over 800 participants in the United States and China. Patients were treated with either deep brain stimulation or non-invasive approaches such as transcranial magnetic stimulation, focused ultrasound, or medication. Healthy subjects and patients with other movement disorders served as comparison groups.
Researchers observed that the most effective treatments were those capable of reducing this hyperconnectivity and normalizing SCAN activity.
More effective non-invasive stimulation
Based on these results, the scientists tested an approach specifically targeting the SCAN using transcranial magnetic stimulation. This non-invasive technique sends magnetic pulses through the skull using a device placed on the head.
In a clinical trial involving 36 patients, half received stimulation precisely targeted at the SCAN site, while the other half received stimulation in adjacent brain areas. After two weeks, 56% of patients in the targeted group showed significant symptom improvement, compared to 22% in the control group. The effectiveness of precise targeting was thus increased 2,5-fold.
This advance could allow for earlier intervention in the disease, without immediately resorting to invasive procedures such as deep brain stimulation, which requires the surgical implantation of electrodes.
Researchers now believe that targeted modulation of the SCAN could not only alleviate symptoms but also potentially influence the course of the disease. Further clinical trials are planned to explore specific applications, particularly for gait disturbances. While these results still need to be confirmed on a larger scale, they redefine the neurological framework of Parkinson's disease and open the prospect of more personalized treatment, centered on brain networks rather than isolated structures.
