Non-canonical role for Lpar1-EGFP subplate neurons in early postnatal mouse somatosensory cortex.

Subplate neurons (SPNs) are thought to play a role in nascent sensory processing in neocortex. To better understand how heterogeneity within this population relates to emergent function, we investigated the synaptic connectivity of Lpar1-EGFP SPNs through the first postnatal week in whisker somatosensory cortex (S1BF). These SPNs comprise of two morphological subtypes: fusiform SPNs with local axons and pyramidal SPNs with axons that extend through the marginal zone. The former receive translaminar synaptic input up until the emergence of the whisker barrels, a timepoint coincident with significant cell death. In contrast, pyramidal SPNs receive local input from the subplate at early ages but then - during the later time window - acquire input from overlying cortex. Combined electrical and optogenetic activation of thalamic afferents identified that Lpar1-EGFP SPNs receive sparse thalamic innervation. These data reveal components of the postnatal network that interpret sparse thalamic input to direct the emergent columnar structure of S1BF.

A role for GABAergic interneuron diversity in circuit development and plasticity of the neonatal cerebral cortex.

GABAergic interneurons are a highly heterogeneous group of cells that are critical for the mature function and development of the neocortex. In terms of the latter, much attention has focused on the well-established role of parvalbumin (PV+)-expressing, fast spiking, basket cells in determining the critical period plasticity. However recent endeavours have started to shed the light on the contribution of other interneuron subtypes to early circuit formation and plasticity. Data suggests that there are significant interactions between PV+ cells and other interneuron subtypes that regulate circuit development in rodents in the first postnatal week. Moreover, a number of these early interactions are transient which points to an important, distinct role for interneuron diversity in setting up emergent neocortical processing.