Optimization of focality and direction in dense electrode array transcranial direct current stimulation (tDCS)

Area of Science:

• Neuroscience
• Biomedical Engineering
• Computational Modeling

Background:

• Transcranial direct current stimulation (tDCS) non-invasively modulates brain function using scalp electrodes.
• Conventional tDCS with large electrodes offers limited targeting precision.
• Dense electrode arrays (up to 512 electrodes) promise enhanced ROI targeting but require sophisticated pattern optimization.

Purpose of the Study:

• To develop a novel method for calculating optimal electrode stimulus patterns for dense array tDCS.
• To achieve targeted and directional modulation of specific brain regions.
• To ensure subject safety through robust constraint implementation.

Main Methods:

• Optimizing stimulus patterns for dense arrays to maximize directional current density in the region of interest (ROI).
• Implementing flexible safety constraints on current power, individual electrode currents, and total injected current.
• Solving the convex optimization problem efficiently to determine unique, globally optimal electrode patterns.

Main Results:

• Demonstrated solutions for four anatomical ROIs using a realistic head model.
• Compared the novel method with two leading existing approaches, highlighting differences.
• Showcased simulation results detailing the impact of safety constraint bounds on optimized patterns.

Conclusions:

• The proposed optimization method is computationally efficient, adaptable to various safety constraints, and utilizes volume-based ROIs.
• In-depth comparisons reveal relationships between objective criteria and optimized patterns.
• Careful selection of safety constraint bounds can improve current localization and safety in tDCS.