Measuring excitation/inhibition balance through field potentials

Several electroencephalography-based metrics have been proposed to index excitation/inhibition balance (E/I). We used single-unit and local field potential recordings from rat medial prefrontal and orbitofrontal cortex and mouse visual cortex and hippocampus to evaluate four candidate metrics against empirically-measured E/I. While 1/f slope and gamma oscillations showed region and context dependencies, broadband (6-80 Hz) and high gamma (80-150 Hz) power consistently correlated with E/I, supporting their use as proxy measures. If at least 30 minutes' data from medial prefrontal cortex were used per animal, broadband power could rank the animals by their E/I ratio, suggesting it could be used as an individual differences measure.