Enabling Electric Field Model of Microscopically Realistic Brain.

Area of Science:

• Neuroscience
• Computational Biology
• Biophysics

Background:

• Modeling brain stimulation is crucial for understanding neuronal activation.
• Previous models often assumed macroscopic homogeneity, neglecting microscopic details.
• Advancements in imaging and analysis enable detailed microscopic modeling.

Purpose of the Study:

• To create the largest map of extracellular electric field distributions in a mouse visual cortex sample.
• To investigate the impact of microscopic electric field perturbations on neuronal activation thresholds.
• To validate macroscopic models for transcranial stimulation.

Main Methods:

• Automated analysis of serial section electron microscopy images.
• Computation of microscopic electric field perturbations using the boundary element fast multipole method.
• Mapping extracellular electric field distributions at the cellular level.

Main Results:

• Generated the largest extracellular electric field map to date (250 × 140 × 90 μm³).
• Microscopic field perturbations ('electric field spatial noise') had a modest effect (<10% average change) on neuronal activation thresholds.
• Justified the 'invisible neuron' assumption in macroscopic brain models for TMS and TES.

Conclusions:

• Microscopic details have a limited impact on overall neuronal activation thresholds.
• Macroscopic models are sufficient for predicting stimulation effects in non-invasive brain stimulation.
• Future work should incorporate microcapillary networks and complex stimulation patterns.