Inhibitory Control of Cortical Activity in vivo
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The cerebral cortex is the largest and most complicated structure of the mammalian brain. The cortex generates many regimes of spontaneous and sensory evoked activity. What are the cellular and circuit mechanisms that determine these regimes? What consequences do they have for sensory processing? And how do these mechanisms vary across behavioral states? To address these questions, I will present three electrophysiological studies of spiking and sub-threshold (synaptic) activity recorded from specific cortical neuron types in vivo. First, I will show that cortical excitation and inhibition closely balance each other during ongoing spontaneous activity. I will next show how inhibitory circuits are recruited to produce reliable and precise cortical activity during naturalistic visual stimulation. Finally, I will show that in the awake cortex, the specific activation of inhibitory circuits dramatically sharpens the spatial and temporal resolution of visual processing. This enhanced role of inhibition during wakefulness shapes how excitatory neuron populations relate to sensory events. Taken together, these studies suggest that cortical inhibitory circuits play the dominant role in rapid modulation of sensory processing according to the demands of the environment and behavior.