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Abstract:
Fast oscillations in cortical circuits critically depend on GABAergic
interneurons. Which interneuron types and populations can drive
different cortical rhythms, however, remains unresolved and may
depend on brain state. Here, we measured the sensitivity of different GABAergic interneurons in prefrontal cortex under conditions
mimicking distinct brain states. While fast-spiking neurons always
exhibited a wide bandwidth of around 400 Hz, the response properties of spike-frequency adapting interneurons switched with the
background input’s statistics. Slowly fluctuating background activity, as typical for sleep or quiet wakefulness, dramatically boosted
the neurons’ sensitivity to gamma and ripple frequencies. We
developed a time-resolved dynamic gain analysis and revealed
rapid sensitivity modulations that enable neurons to periodically
boost gamma oscillations and ripples during specific phases of
ongoing low-frequency oscillations. This mechanism predicts these
prefrontal interneurons to be exquisitely sensitive to highfrequency ripples, especially during brain states characterized by
slow rhythms, and to contribute substantially to theta-gamma
cross-frequency coupling.
