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GABAergic interneurons play key roles in cortical circuits, yet little is known about their early connectivity. Here we use glutamate uncaging and a novel optogenetic strategy to track changes in the afferent and efferent synaptic connections of developing neocortical interneuron subtypes. We find that Nkx2-1-derived interneurons possess functional synaptic connections before emerging pyramidal cell networks. Subsequent interneuron circuit maturation is both subtype and layer dependent. Glutamatergic input onto fast spiking (FS), but not somatostatin-positive, non-FS interneurons increases over development. Interneurons of both subtype located in layers (L) 4 and 5b engage in transient circuits that disappear after the somatosensory critical period. These include a pathway mediated by L5b somatostatin-positive interneurons that specifically targets L4 during the first postnatal week. The innervation patterns of immature cortical interneuron circuits are thus neither static nor progressively strengthened but follow a layer-specific choreography of transient connections that differ from those of the adult brain.

Original publication

DOI

10.1038/ncomms10584

Type

Journal article

Journal

Nat Commun

Publication Date

04/02/2016

Volume

7

Keywords

Animals, Animals, Newborn, Cluster Analysis, GABAergic Neurons, Green Fluorescent Proteins, Immunohistochemistry, Interneurons, Mice, Neocortex, Nerve Net, Nuclear Proteins, Optogenetics, Patch-Clamp Techniques, Principal Component Analysis, Pyramidal Cells, Synapses, Thyroid Nuclear Factor 1, Transcription Factors