Selective Maturation of Temporal Dynamics of Intracortical Excitatory Transmission at the Critical Period Onset

•Temporal dynamics of intracortical excitatory synapses mature at critical period onset•Dynamics of cortical inhibitory synapses and thalamocortical inputs are unchanged•This selective modulation depends on early visual experience•Ubiquitous reduction of presynaptic release underlies the selective modulation.

SummaryAlthough the developmental maturation of cortical inhibitory synapses is known to be a critical factor in gating the onset of critical period (CP) for experience-dependent cortical plasticity, how synaptic transmission dynamics of other cortical synapses are regulated during the transition to CP remains unknown. Here, by systematically examining various intracortical synapses within layer 4 of the mouse visual cortex, we demonstrate that synaptic temporal dynamics of intracortical excitatory synapses on principal cells (PCs) and inhibitory parvalbumin- or somatostatin-expressing cells are selectively regulated before the CP onset, whereas those of intracortical inhibitory synapses and long-range thalamocortical excitatory synapses remain unchanged. This selective maturation of synaptic dynamics results from a ubiquitous reduction of presynaptic release and is dependent on visual experience. These findings provide an additional essential circuit mechanism for regulating CP timing in the developing visual cortex.

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