New Paper: Enabling electric field model of microscopically realistic brain

A new lab paper in Brain Stimulation Journal challenges a foundational assumption in computational models of brain stimulation (neuromodulation/electrical stimulation). Rather than suggest prior predictions were wrong, this paper shows how the suitability of this foundational assumption can be evaluated in any application (FES, SCS, DBS, TMS, tDCS, tACS, ETC, TI...). So this will be interesting...

"Enabling electric field model of microscopically realistic brain" is 1) First to model brain stimulation with a realistic microscopic extracellular environment; 2) Showing microscopic perturbations of the electric field by neighboring cell structures; 3) Applicable to all electrical/magnetic stimulation.

This pipeline contrasts with decades of convention which: a) First ignores all microscopic structures, with each region represented by a macroscopically averaged resistivity; b) Only after the macroscopic electric field is predicted (with FEM) are isolated neurons “reinserted” to model their response. Justified or not, this convention is universal from classical modeling studies to the most advanced recent studies because it was *computationally necessary*. The reliability of this convention depends on the physical presence of cellular structures (such as neurons, glia, vessels) NOT impacting the generation of electric fields in the first place. This idea is challenged by the sheer packing of cells - as quantified by scanning electron microscopy.

For the stimulation conditions & limited structures considered in this first study, electric fields were microscopically perturbed by neighboring cells but this only modestly influenced stimulation thresholds (~10%). This provides tentative support that the foundational modeling assumption that ignores the physical presence of neurons is sufficiently precise. But there remain many stimulation technologies (specialty waveforms) & brain structures (blood vessels, synaptic clefts) to consider. This paper provides the pipeline for such ongoing research.

Reference: Zhen Qi, Gregory M Noetscher, Alton Miles, Konstantin Weise, Thomas R Knösche, Cameron R Cadman, Alina R Potashinsky, Kelu Liu, William A Wartman, Guillermo Nunez Ponasso, Marom Bikson, Hanbing Lu, Zhi-De Deng, Aapo R Nummenmaa, Sergey N Makaroff. Enabling electric field model of microscopically realistic brain. Brain Stimulation. 18(1):77-93. doi: 10.1016/j.brs.2024.12.1192