Dissecting executive control circuits with neuron types.

Executive control supports our ability to behave flexibly in accordance with a given situation. In order to fully understand how cortical circuits achieve this task, we need to determine the intrinsic physiological and connection profiles of neuron types and analyze their functional roles during behavior. This article introduces current knowledge regarding neuron type classification in the cortex and reviews our understanding of how each neuron type is incorporated in the functional cortical circuit to implement executive control. Recent work using neuron-type specific imaging/recording has begun to reveal significant functional organizations of pyramidal neurons and their subtypes depending on the layers and long-range projection targets. GABAergic interneurons also make crucial contributions to executive control in a subtype-specific manner. Vasoactive intestinal peptide (VIP)-positive interneurons are preferentially recruited by top-down inputs from higher-order cortical regions and amplify the signals in pyramidal neurons by inhibiting other interneuron subtypes. Particularly in the prefrontal cortex, one of the hierarchically highest cortices, executive control signals are regulated by the VIP neuron-mediated disinhibition and robustly maintained through recurrent connections at a long time scale. The differences and commonalities in the functional organization between sensory areas and the prefrontal cortex are discussed.