Assessing the direct effects of deep brain stimulation using embedded axon models.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Computational Biology

Background:

• Deep brain stimulation (DBS) is a key therapy for Parkinson's disease.
• Understanding the precise spread of electrical stimulation in the brain is crucial for optimizing DBS efficacy.
• Previous models lacked detailed anatomical and electrical property considerations.

Purpose of the Study:

• To model the spatial extent of direct neuronal activation by DBS.
• To investigate the influence of brain tissue properties on electrical field spread.
• To identify brain regions activated by DBS targeting the subthalamic nucleus (STN).

Main Methods:

• Developed a geometrically realistic finite element electrical model.
• Incorporated anisotropic and inhomogeneous tissue conductivities.
• Utilized multi-compartment axon models with anatomically consistent geometry and orientation.

Main Results:

• Simulations showed axonal activation up to 4 mm from the stimulated STN.
• Activation occurred in the fields of Forel (FF), internal capsule (IC), substantia nigra (SN), and zona incerta (ZI).
• Sensitivity analysis confirmed consistent activation in FF and IC.

Conclusions:

• Direct axonal activation outside the STN occurs with typical DBS parameters.
• The spread of activation into surrounding white matter tracts (IC, FF) and nuclei (SN, ZI) is significant.
• These findings suggest that non-target brain regions contribute to the therapeutic benefits of DBS for Parkinsonian symptoms.