Severe behavioural deficits in psychiatric diseases such as autism and schizophrenia have been hypothesized to arise from elevations in the cellular balance of excitation and inhibition (E/I balance) within neural microcircuitry. This hypothesis could unify diverse streams of pathophysiological and genetic evidence, but has not been susceptible to direct testing. Here we design and use several novel optogenetic tools to causally investigate the cellular E/I balance hypothesis in freely moving mammals, and explore the associated circuit physiology. Elevation, but not reduction, of cellular E/I balance within the mouse medial prefrontal cortex was found to elicit a profound impairment in cellular information processing, associated with specific behavioural impairments and increased high-frequency power in the 30-80 Hz range, which have both been observed in clinical conditions in humans. Consistent with the E/I balance hypothesis, compensatory elevation of inhibitory cell excitability partially rescued social deficits caused by E/I balance elevation. These results provide support for the elevated cellular E/I balance hypothesis of severe neuropsychiatric disease-related symptoms.
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Acknowledgements We thank the K.D., P.H. and J.R.H. laboratories for discussions on the manuscript. We are grateful to S. Pak, Z. Chen and C. Perry for technical assistance. O.Y. is supported by the Human Frontier Science Program. L.E.F. is supported by the Stanford MSTP program. P.H. is supported by the DFG (HE3824/9-1 and 17-1, Cluster of Excellence: Unifying Concepts in Catalysis), and K.D. by NIMH, NIDA, NINDS, the DARPA REPAIR program, CIRM and the Yu, Woo, Snyder and Keck Foundations.