Sex and Electrode Configuration in Transcranial Electrical Stimulation

Area of Science:

• Neuroscience
• Biomedical Engineering
• Medical Imaging

Background:

• Transcranial electrical stimulation (tES) is a non-invasive neuromodulation technique with potential therapeutic applications.
• Significant variability in tES treatment outcomes necessitates investigation into factors influencing current delivery.
• Individual differences in cranial morphology and tissue conductivity are hypothesized contributors to this variability.

Purpose of the Study:

• To model electrical current density at cortical targets under different tES electrode configurations and intensities.
• To assess the impact of individual anatomical variations on current delivery.
• To determine if electrode configuration and individual differences explain variability in tES outcomes.

Main Methods:

• Validated MRI modeling procedures were used to simulate electrical current flow in 23 subjects.
• Three common tES electrode configurations (non-cephalic, bi-cranial, ring) were modeled.
• Simulations were performed at three current intensities (0.5, 1.0, and 2.0 mA) targeting frontal and temporal cortical regions.

Main Results:

• Electrode configurations produced up to a ninefold difference in mean current densities delivered to the brain.
• The non-cephalic configuration delivered the highest current density, while the ring configuration delivered the least.
• Female subjects received significantly less current to the brain compared to male subjects.

Conclusions:

• Individual variations in cranial anatomy and tissue conductivity, alongside differing electrode configurations, significantly influence tES current delivery.
• These factors likely account for a substantial portion of the variability observed in tES clinical outcomes.
• Optimizing electrode selection and considering individual differences are crucial for reliable and effective tES neuromodulation.