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New Brain Network SCAN Offers Hope for Parkinson's Treatment

Recent research points to SCAN as a target for therapies; TMS shows promise in reducing tremors in Parkinson’s patients.
G
Gopi
••7 mins read
New brain network (SCAN) offers promising precise targets 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 PointFigure
Global Parkinson's patients1 crore+
Estimated patients in India58 lakh
Study published inNature, 2025
Patients analysed in study863
Dataset gathered since2016
TMS trial participants18 Parkinson's patients
Trial result timelineSignificant 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

TreatmentMechanismLimitation
LevodopaDopamine precursor — replenishes dopamineVariable effect; prolonged use causes uncontrolled movements
Deep Brain Stimulation (DBS)Electrodes surgically implanted in brain regionsExpensive, invasive, requires surgery
Transcranial Magnetic Stimulation (TMS)Magnetic fields stimulate nerve cells non-invasivelyExperimental; precise brain targets not yet established

Key Concepts

ConceptExplanation
Motor CortexSurface brain region controlling muscular activity of specific body parts
Motor-Effector AreasSpecific zones in motor cortex controlling individual body parts (arm, foot, mouth)
Higher Order NetworksLarge-scale brain networks integrating information for complex functions like planning and attention
SCANSomatic Cognitive Action Network — newly identified brain network coordinating movement across regions
Basal GangliaDeep 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
BiomarkerA 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

FindingDetail
SCAN over-connectivityAbnormally strengthened in Parkinson's patients
SpecificityNot seen in ALS (another motor disorder) — suggests Parkinson's-specific mechanism
Treatment correlationWhen treatments worked, SCAN over-connectivity consistently reduced — across DBS, levodopa, and TMS
New biomarkerSCAN 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

ExpertConcern
Alfonso Fasano, University of TorontoParkinson's is heterogeneous — framing it purely as a SCAN disorder is oversimplistic; other conditions like parkinsonism may show similar network abnormalities
Prashanth Kukkle, BengaluruSCAN 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.

Quick Q&A

Everything you need to know

Parkinson’s disease is a progressive neurodegenerative disorder that primarily affects movement due to the loss of dopamine-producing neurons in the brain, particularly in the basal ganglia. Dopamine is essential for smooth and coordinated muscle activity. As its levels decline, patients experience symptoms such as tremors, rigidity, bradykinesia (slowness of movement), and postural instability.

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
Example: A patient may take several minutes to perform a simple activity like tying shoelaces, reflecting how the disease disrupts motor planning and execution. Thus, Parkinson’s is not merely a movement disorder but a condition that deeply impacts functional autonomy and dignity.

Current treatments for Parkinson’s disease primarily focus on symptom management rather than curing or halting disease progression. The most widely used drug, levodopa, temporarily replenishes dopamine levels and improves motor symptoms. However, its effectiveness diminishes over time, and prolonged use often leads to side effects such as dyskinesia (involuntary movements).

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
Example: Two patients on the same levodopa regimen may show vastly different outcomes, highlighting the unpredictable nature of treatment response.

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.

The discovery of the Somatic Cognitive Action Network (SCAN) marks a paradigm shift in understanding Parkinson’s disease. Traditionally, the focus was on motor-effector regions of the brain that control specific body parts. However, this approach failed to fully explain the coordination deficits seen in patients.

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
Example: Instead of viewing walking difficulty as a muscle control issue, SCAN explains it as a failure of integrated planning and execution across brain regions.

Thus, SCAN redefines Parkinson’s as a network disorder, opening new avenues for targeted and effective therapies.

Precision Functional Mapping (PFM) is an advanced neuroimaging technique that allows scientists to map brain activity at the level of individual brains, rather than relying on averaged data. Traditional imaging methods often produced generalized maps, which lacked the specificity needed for personalized 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
Example: Instead of applying brain stimulation to a general region, doctors can now target specific SCAN nodes unique to a patient, increasing treatment effectiveness.

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.

Potential: The identification of SCAN offers a promising target for both non-invasive and minimally invasive therapies. Techniques like Transcranial Magnetic Stimulation (TMS) can directly modulate SCAN activity, potentially improving symptoms such as tremors and rigidity. Early trials have shown significant improvements within weeks, indicating strong clinical potential.

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
Example: While SCAN-targeted TMS showed improvement in a small trial, larger and longer studies are needed before it becomes standard care.

Thus, while SCAN-based therapies represent a breakthrough in concept, their translation into routine clinical practice requires cautious validation and refinement.

A network-level understanding of the brain recognises that functions like movement, cognition, and emotion arise from interactions between multiple regions rather than isolated areas. This approach has transformative implications for treatment.

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.

A recent study published in Nature provides a compelling case study on the clinical relevance of SCAN. Researchers analysed brain data from 863 Parkinson’s patients using precision functional mapping. They discovered that SCAN exhibited abnormal over-connectivity with the basal ganglia, a hallmark of Parkinson’s pathology.

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.

Attribution

Original content sources and authors

SP
Sheetal Potdar
TH
The Hindu
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