Inhibitory Interneurons Regulate Temporal Precision and Correlations in Cortical Circuits

GABAergic interneurons, which are highly diverse, have long been thought to contribute to the timing of neural activity as well as to the generation and shaping of brain rhythms. GABAergic activity is crucial not only for entrainment of oscillatory activity across a neural population, but also for precise regulation of the timing of action potentials and the suppression of slow-timescale correlations. The diversity of inhibition provides the potential for flexible regulation of patterned activity, but also poses a challenge to identifying the elements of excitatory–inhibitory interactions underlying network engagement. This review highlights the key roles of inhibitory interneurons in spike correlations and brain rhythms, describes several scales on which GABAergic inhibition regulates timing in neural networks, and identifies potential consequences of inhibitory dysfunction. The intrinsic and synaptic properties of GABAergic interneurons shape their impact on temporal patterns in the local circuit. Synaptic inhibition enhances short-timescale correlations in spiking, such as spike synchrony, but suppresses long-timescale correlations, such as noise correlations. Different inhibitory interneuron populations, including parvalbumin and somatostatin cells, may engage distinct rhythms in the cortex. The emergence of circuit timing characteristics is shaped on the developmental timescale by multiple interneuron populations.