Atlas-based electrical source imaging for mouse EEG: Application to an Fmr1 knockout model.

Electrical source imaging (ESI) reconstructs where in the brain a scalp EEG signal arises. It is routine in humans but unestablished in the mouse, whose brain is some 3000 times smaller where it is not obvious that a sparse array can separate one region from another. We built an atlas-based ESI pipeline for 30-channel mouse EEG and tested it against simulated dipoles, across 18 combinations of source space, head model and inverse operator, with conductivity and noise sweeps. The best, a region-of-interest source space with an ellipsoid head model and sLORETA, recovered superficial sources to a mean error of 0.93 mm, rising to 5.08 mm at depth. We then applied it to resting EEG from male Fmr1 knockout (n = 18) and wild-type (n = 17) mice. Gamma power was elevated in the knockouts (Low Gamma q = 0.004, standardized mean difference 1.02; High Gamma q = 0.004, 0.67) and localized to six parcels, three of them in both bands. Relative power in Delta, Theta and High Gamma, and both aperiodic parameters, varied by region (q < 0.001 to 0.035). The electrode analysis recovered neither the Delta pattern nor any named structure. The gamma findings survived adjustment for acquisition cohort (p = 0.001 and 0.002). Simulation bounds what the pipeline recovers and which region it assigns activity to, but cannot show that a labeled region is the true source in a live animal. Replication across recording systems, sex, age and injection-naive animals is needed.