Individual differences in transcranial electrical stimulation current density.

Area of Science:

• Neuroscience
• Medical Imaging
• Biophysics

Background:

• Transcranial electrical stimulation (TCES) shows therapeutic potential for various conditions.
• Accurate prediction of current density distribution within individual head anatomy remains a challenge.
• Current TCES application often relies on standardized systems like the 10-20 system, potentially limiting efficacy.

Purpose of the Study:

• To predict and verify TCES current densities using patient-specific models.
• To quantify the variability of current distributions across individuals.
• To assess the utility of MRI-based modeling for optimizing TCES.

Main Methods:

• Experiment 1: Estimated conductivity from MRI data and compared modeled scalp surface current density with direct measurements in 3 subjects.
• Experiment 2: Simulated TCES (2 mA) using virtual electrodes on 18 subjects' scalps across 4 electrode configurations.
• Calculated current densities for 75 brain regions in patient-specific MRI-based models.

Main Results:

• Experiment 1 showed a strong correlation (r = .93) between modeled and measured external current.
• Experiment 2 revealed significant individual variability in current density, with up to ten-fold differences near electrodes.
• Simulated current reached all brain regions, with two-fold differences observed in distant areas like the hypothalamus.

Conclusions:

• MRI-based modeling accurately predicts TCES current densities in individual brains.
• Significant inter-subject variability in current distribution necessitates individualized approaches.
• Patient-specific MRI-based modeling offers a more accurate alternative to the 10-20 system for precise TCES.