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In early postnatal life,inhibitory circuits are readily sculpted by sensory experience to enable cortical maturation and map plasticity.In the primary auditory cortex(A1),in particular,the development of the tonotopic map is governed by the experience-dependent refinement of inhibitory synaptic strength across the whole receptive field.However,not all stimulus features are topographically represented in the cortex,for example,features of thetemporal stimulus domain7.Whether and how inhibitory circuits are involved in cortical processing of temporal features,such as stimulus sequences,in the context of developmentremains unknown.Here we show that,in developing rat A1,the inhibitory time courseand its plasticity play a crucial role in the maturation of temporal sequence processing.By applyingwhole-cell recordings in vivo,we find that,within the range of ethological sound repetition rates,even low-repetition-rate stimuli evoke sustained inhibition in developing rat A1.This long-lasting inhibition arises from the remarkably long decay time of inhibitory conductances early in maturation and suppresses cortical responses to successive stimuli.Strikingly,only 3-5 minutes of exposure to high-or low-repetition-rate stimuli dramatically shortens or prolongs the time course of inhibition.The exposure-dependent shortening of the inhibitory time course during maturation enables a neuron to respond to higher stimulus repetition rates due to the emergence of a more adult-like integration pattern of excitation and inhibition.Thus,our results reveal a novel form of inhibitory synaptic plasticity,highlighting the unique contribution of inhibitory temporal dynamics to the maturation ofcortical temporal processing.