New Brain Network SCAN Offers Hope for Parkinson's Treatment
Introduction
A landmark Nature (2025) study has identified the Somatic Cognitive Action Network (SCAN) as a key brain network abnormally strengthened in Parkinson's disease — opening a new frontier for precise, non-invasive treatment at a time when existing therapies remain inadequate for crores of patients worldwide.
"In future, there will be both non-invasive and minimally invasive neuromodulatory therapies aimed directly at SCAN in a personalised manner." — Nico Dosenbach, Neurologist, Washington University School of Medicine
| Data Point | Figure |
|---|---|
| Global Parkinson's patients | 1 crore+ |
| Estimated patients in India | 58 lakh |
| Study published in | Nature, 2025 |
| Patients analysed in study | 863 |
| Dataset gathered since | 2016 |
| TMS trial participants | 18 Parkinson's patients |
| Trial result timeline | Significant improvement within 2 weeks |
Background and Context
What is Parkinson's Disease? Parkinson's is a progressive neurodegenerative disorder characterised by:
- Tremors, rigidity, and slowness of movement
- Difficulty initiating and stopping actions
- Postural instability worsening over time
It is caused primarily by the loss of dopamine-producing neurons in the brain's basal ganglia — a cluster of structures critical for movement coordination.
Limitations of Existing Treatments
| Treatment | Mechanism | Limitation |
|---|---|---|
| Levodopa | Dopamine precursor — replenishes dopamine | Variable effect; prolonged use causes uncontrolled movements |
| Deep Brain Stimulation (DBS) | Electrodes surgically implanted in brain regions | Expensive, invasive, requires surgery |
| Transcranial Magnetic Stimulation (TMS) | Magnetic fields stimulate nerve cells non-invasively | Experimental; precise brain targets not yet established |
Key Concepts
| Concept | Explanation |
|---|---|
| Motor Cortex | Surface brain region controlling muscular activity of specific body parts |
| Motor-Effector Areas | Specific zones in motor cortex controlling individual body parts (arm, foot, mouth) |
| Higher Order Networks | Large-scale brain networks integrating information for complex functions like planning and attention |
| SCAN | Somatic Cognitive Action Network — newly identified brain network coordinating movement across regions |
| Basal Ganglia | Deep brain structures critical for movement — abnormally connected to SCAN in Parkinson's patients |
| Precision Functional Mapping (PFM) | Advanced brain imaging technique mapping individual brains at high resolution |
| Biomarker | A measurable biological indicator of a disease — SCAN over-connectivity is a new biomarker for Parkinson's |
Discovery of SCAN: The Science
From Penfield Map to Precision Functional Mapping
- A century ago, neurosurgeon Wilder Penfield mapped the motor cortex by electrically stimulating brain surfaces in awake patients — creating a body map across the cortex.
- This map was later refined by Nico Dosenbach using Precision Functional Mapping (PFM) — which maps individual brains rather than averaging data across populations.
"Previously, most imaging studies relied on averaging data across individuals. It's like averaging the faces of 100 people — you would end up with a cartoon face, not a real face." — Nico Dosenbach, Washington University
The Three-Dot Pattern
- Using PFM in 2023, Dosenbach's team discovered three additional activation zones appearing whenever any unrelated body part was stimulated — interspersed between effector regions for arm, foot, and mouth.
- This consistent pattern across individuals suggested an entirely new organisational principle in the motor cortex — later named SCAN.
SCAN and Parkinson's Disease: Key Findings
The Study
- Analysed functional MRI scans and electrocorticographs of 863 Parkinson's patients — one of the largest datasets of its kind, gathered since 2016.
- Led by Hesheng Liu, Changping Laboratory, Beijing, published in Nature.
Core Finding
"In Parkinson's disease patients, the SCAN network shows pathological abnormal strengthening of connections with the basal ganglia and thalamus." — Hesheng Liu, Lead Author
| Finding | Detail |
|---|---|
| SCAN over-connectivity | Abnormally strengthened in Parkinson's patients |
| Specificity | Not seen in ALS (another motor disorder) — suggests Parkinson's-specific mechanism |
| Treatment correlation | When treatments worked, SCAN over-connectivity consistently reduced — across DBS, levodopa, and TMS |
| New biomarker | SCAN over-connectivity with basal ganglia = network-level biomarker for Parkinson's |
Clinical Implications: The TMS Trial
- 18 Parkinson's patients randomly assigned to receive TMS directed at SCAN regions.
- Compared to control group receiving TMS at effector regions — SCAN-targeted group showed significantly less tremors, rigidity, slowness, and instability within just two weeks.
- Result: SCAN-targeted TMS is a promising, non-invasive, personalised therapy on the horizon.
"Being superficially located in the cortex, SCAN is easily accessible by TMS for non-invasive modulation." — Prashanth Kukkle, Consultant Neurologist, Bengaluru
Critical Perspectives
| Expert | Concern |
|---|---|
| Alfonso Fasano, University of Toronto | Parkinson's is heterogeneous — framing it purely as a SCAN disorder is oversimplistic; other conditions like parkinsonism may show similar network abnormalities |
| Prashanth Kukkle, Bengaluru | SCAN is a newly discovered region not yet in standard medical textbooks — early evidence is promising but clinical translation uncertain |
India's Policy Framework for Parkinson's Disease
India does not have a dedicated national policy specifically for Parkinson's disease. However, several broader frameworks partially address it:
What Exists
1. Rights of Persons with Disabilities Act, 2016 (RPwD Act) Parkinson's disease is recognised as a disability under this Act — making patients eligible for disability certificates, financial assistance, pension transfers, and other welfare benefits. However, the process of disability certification for Parkinson's patients remains cumbersome and poorly implemented, particularly at primary and secondary healthcare levels where motor assessment scales are not widely used by non-neurologists.
2. National Programme for Non-Communicable Diseases (NP-NCD) Neurological disorders fall under this programme broadly, but Parkinson's has no targeted sub-programme unlike cancer, diabetes, or cardiovascular diseases.
3. Ayushman Bharat / PM-JAY Covers hospitalisation costs including DBS surgery in empanelled hospitals — but access remains limited given the scarcity of specialist centres.
4. National Parkinson Network (NPN) — 2024 The inaugural meeting of India's National Parkinson Network was held on December 13, 2024 at AIIMS New Delhi — bringing together movement disorder experts, patient representatives, and policy makers to identify gaps and support country-specific solutions for Parkinson's care. This is chaired by Prof. Pramod Pal of NIMHANS, Bengaluru.
Critical Gaps
- No dedicated national Parkinson's disease policy or programme
- Significant lack of awareness, limited access to specialist treatment, and financial barriers remain major challenges for Parkinson's patients in India.
- Low- and middle-income countries like India face limited access to neurologists, diagnostic tools, and long-term care facilities — necessitating region-specific policy planning.
- Levodopa is available but DBS — the more effective surgical option — is expensive and accessible only in large urban hospitals
- Rural India has higher Parkinson's prevalence than urban India (41 vs 14 per 1,00,000) yet far lower access to care
Bottom Line for UPSC India's Parkinson's governance is reactive and fragmented — disability law provides a safety net on paper, but implementation gaps, neurologist shortages, and the absence of a dedicated national programme leave most patients — especially in rural areas — without adequate care. The SCAN discovery's promise of affordable TMS therapy could be transformative if India proactively invests in neuroscience infrastructure and integrates neurological disorders more explicitly into its NCD policy architecture.
Implications for Health Governance
For India
- India bears a significant Parkinson's burden with limited access to expensive DBS therapy — a non-invasive TMS alternative targeting SCAN could be transformative for public health.
- Strengthens the case for investment in neuroscience research under India's biomedical R&D framework.
- Relevant to National Programme for Non-Communicable Diseases (NP-NCD) — neurological disorders must be integrated more explicitly.
For Global Health
- Offers a potential low-cost, scalable alternative to surgical DBS — particularly relevant for low- and middle-income countries.
- Advances precision medicine — personalised brain mapping (PFM) could reshape neurology beyond Parkinson's.
Conclusion
The discovery of SCAN and its abnormal over-connectivity in Parkinson's disease represents a paradigm shift in neuroscience — moving from localised motor-effector targeting to understanding Parkinson's as a network-level disorder. The preliminary TMS trial results are encouraging, and the convergence of precision brain mapping, large-scale clinical data, and non-invasive stimulation technology suggests a new therapeutic era is approaching. However, scientific caution is warranted — SCAN's role in the heterogeneous spectrum of Parkinson's must be validated across larger, more diverse populations before it enters routine clinical practice. For India's health governance, the promise of affordable non-invasive neuromodulation must be matched by proactive investment in neurological research and infrastructure.
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GS2HealthcareQuick Q&A
What is Parkinson’s disease, and how does it affect motor coordination and daily life?
In daily life, this translates into significant functional challenges. Tasks that are normally automatic—such as walking, turning, or buttoning a shirt—require conscious planning and effort. Patients often struggle to initiate or stop movements, leading to phenomena like “freezing of gait.” Over time, these impairments worsen, affecting independence and quality of life.
Broader implications:
- Increased caregiver burden and healthcare costs
- Psychological issues such as depression and anxiety
- Reduced productivity and social participation
Why have existing treatments for Parkinson’s disease been considered inadequate?
Another major therapy is Deep Brain Stimulation (DBS), which involves surgically implanting electrodes in specific brain regions. While effective in certain patients, DBS is invasive, expensive, and not universally accessible. Additionally, it does not work equally well for all symptoms, particularly non-motor aspects.
Limitations of current therapies:
- Lack of precision in targeting underlying neural circuits
- Variable patient response due to disease heterogeneity
- Inability to address coordination deficits fully
Thus, the inadequacy stems from a limited understanding of the complex brain networks involved, which recent research on SCAN seeks to address by identifying more precise therapeutic targets.
How has the discovery of the Somatic Cognitive Action Network (SCAN) changed our understanding of Parkinson’s disease?
SCAN represents a higher-order brain network that integrates motor, cognitive, and planning functions. It connects with deeper brain structures such as the basal ganglia and thalamus, which are central to Parkinson’s pathology. The study found that in Parkinson’s patients, SCAN exhibits abnormal over-connectivity, disrupting coordinated movement.
Key implications:
- Moves focus from isolated brain regions to network-level dysfunction
- Explains why patients struggle with initiating and coordinating movements
- Provides a unified framework linking motor and cognitive symptoms
Thus, SCAN redefines Parkinson’s as a network disorder, opening new avenues for targeted and effective therapies.
How does precision functional mapping (PFM) contribute to advances in neurological research and treatment?
PFM provides high-resolution, individualized brain maps, revealing subtle patterns such as the “three-dot” SCAN structure in the motor cortex. This has enabled researchers to identify previously unknown networks and understand their role in diseases like Parkinson’s.
Significance of PFM:
- Enhances accuracy in identifying therapeutic targets
- Enables personalized medicine approaches
- Improves outcomes in interventions like TMS and DBS
In essence, PFM shifts neurology from a one-size-fits-all approach to precision medicine, which is crucial for complex and heterogeneous disorders like Parkinson’s disease.
Critically analyse the potential and limitations of SCAN-based therapies for Parkinson’s disease.
Advantages include:
- Non-invasive and relatively cost-effective compared to DBS
- Targeted intervention at network level
- Potential for personalized treatment using PFM
Limitations: However, several challenges remain. Parkinson’s disease is heterogeneous, meaning not all patients may benefit equally. Additionally, SCAN is a newly discovered network and is not yet fully validated across diverse populations.
Concerns include:
- Oversimplification of Parkinson’s as a single-network disorder
- Lack of long-term clinical evidence
- Overlap with other neurological conditions like dystonia
Thus, while SCAN-based therapies represent a breakthrough in concept, their translation into routine clinical practice requires cautious validation and refinement.
Can you illustrate with examples how network-level understanding of the brain can improve treatment outcomes in neurological disorders?
Example in Parkinson’s disease: SCAN-based targeting allows therapies like TMS to modulate entire networks responsible for coordination, rather than just stimulating motor regions. This leads to more comprehensive symptom relief, including improvements in planning and execution of movement.
Other examples:
- Depression: Targeting the default mode network using TMS has improved treatment-resistant cases
- Epilepsy: Network analysis helps identify seizure propagation pathways for surgical intervention
- Stroke rehabilitation: Enhancing connectivity between motor and cognitive networks aids recovery
This approach also enables personalized medicine, as individual brain networks can vary significantly. Treatments can be tailored to each patient’s unique neural architecture.
Thus, shifting from a region-centric to a network-centric model represents a major advancement in neuroscience, improving both diagnostic accuracy and therapeutic efficacy.
Discuss a case study from recent research that demonstrates the clinical relevance of SCAN in Parkinson’s disease treatment.
To test its therapeutic potential, a preliminary trial was conducted where 18 patients were randomly assigned to receive TMS targeting SCAN regions. The control group received stimulation in traditional motor-effector areas. Within two weeks, the SCAN-targeted group showed significant improvements in tremors, rigidity, and movement speed.
Key takeaways:
- SCAN can serve as a reliable biomarker for Parkinson’s
- Targeted neuromodulation can yield rapid clinical benefits
- Network-based interventions outperform traditional approaches
Limitations: The study was small-scale and short-term, necessitating larger trials for validation.
This case study highlights how integrating advanced imaging, network science, and clinical trials can accelerate breakthroughs in treatment, offering hope for more effective and accessible therapies in the future.
The discovery of SCAN in Parkinson's offers a new frontier for non-invasive treatment in a disease with limited current therapies.
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