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Updated: Oct 16, 2025
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A Novel Approach for Documenting Phosphenes Induced by Transcranial Magnetic Stimulation
Published on: April 1, 2010
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Evaluating Current Density Modeling of Non-Invasive Eye and Brain Electrical Stimulation Using Phosphene Thresholds
Summary
This study validates computer models for estimating brain current flow using phosphene threshold measurements. Findings confirm phosphenes originate in the retina and support using these models for real-world current flow estimation.
Area of Science:
- Neuroscience
- Biophysics
- Computational Modeling
Background:
- Direct measurement of current flow in the brain is challenging.
- Current density distribution models are used to estimate current flow during stimulation.
- A method is needed to validate these models against physiological data.
Purpose of the Study:
- To evaluate if current flow modeling correlates with physiological signs of true current distribution.
- To determine if phosphene thresholds (PTs) from transcranial alternating current stimulation (tACS) match simulated current densities.
- To provide in vivo evidence for the validity of head model-based current flow simulations.
Main Methods:
- Phosphene threshold measurements were conducted in 15 healthy males using various tACS electrode montages.
- Subjects reported phosphene appearance and localization.
- Head models were created using multi-modal imaging data and meshed with isotropic conductivities for simulation.
Main Results:
- Lower PTs correlated with higher simulated current levels in unilateral montages.
- Shorter electrode distances to the eye resulted in lower PTs.
- The F7-F8 montage showed the lowest mean PT and variability.
Conclusions:
- Phosphenes are primarily of retinal origin.
- Computer models using head models are valid for estimating current flow in the human eye and brain.
- This study provides the first in vivo evidence supporting these computational models.
