Electric Field Distributions in Brain Stimulation Experimental Setups

The effects of electric brain stimulation are often studied in the lab, for instance to study the optimal field stimuli parameters. Regularly, 'uniform' electric fields are used to stimulate cells and brain networks. In this multiphysics-based simulation study, the extend of the uniformity of lab-generated fields is investigated for some commonly used experimental setups. It is found that the electric fields significantly deviate from uniformity for most situations, even though strictly homogeneous media are used in this study. The spatial variety of electric fields is present especially for studies that include whole-brain slices, such as investigations of network activity. The deviation from uniformity also complicates the measurements of the field magnitude, which is commonly performed by measuring the potential difference between two sensors. In a uniform field, the sensor position does not influence the outcome of the field magnitude measurement. Due to the non-uniformity of the fields in practical setups, however, the sensor position was found to have a significant influence on the perceived field magnitude. We therefore advise authors of experimental papers to provide more details regarding their field generation setup (electrode size, shape, distance, and sensor position), such that the fields can be reconstructed and the spatial variance can be taken into account in follow-up computational modeling studies.