How small electric fields still affect neurons?

Abstract

The effects of transcranial electric field stimulation on neural activity have been studied extensively with in vivo animal experiments. However, to date, these experiments have not adequately characterized electric field magnitudes in the brain. Thus, it is difficult to interpret and link these results to cellular effects observed in vitro, or to behavioral effects observed in humans. There, electric fields are relatively well characterized, either through direct measurement or with calibrated computational current flow models.

To close this gap, we measured electric fields and its effects on neuronal firing rate in vivo in rats, and established calibrated computational models of current flow. The recording equipment was calibrated with measurement and model of a cylindrical agar phantom.

Electric fields grow linearly with current intensity, with 150 µA resulting in 2 V/m in the motor cortex and 1.0 V/m in the hippocampus, and deviating across frequency or animals by no more than 25%. In-vivo field measurements matched detailed computational models of current flow with similar accuracy. Electric fields of 1V/m modulated firing rate by about 5% on average.

Calibrated field measurements show that effects of E fields on firing rate in-vivo are in line with effect sizes of prior in vitro studies and human behavioral studies.

Mihály Vöröslakos

Postdoctoral Researcher

My research interests include translational neuroscience, non-invasive brain stimulation and neuroscience tool development.