Cell type specializations of the vocal-motor cortex in songbirds

The identification of molecular specializations in cortical circuitry supporting complex behaviors, such as learned vocalizations, requires understanding the neuroanatomical context from which these circuits arise. In songbirds, the robust nucleus of the arcopallium (RA) provides the sole descending projection for fine motor control of vocalizations. Using single nuclei transcriptomics and spatial gene expression mapping in zebra finches, we were able to define cell types and molecular specializations that distinguish RA from adjacent regions involved in non-vocal motor and sensory processing. We describe an RA-specific vocal projection neuron, differential composition of inhibitory neuron subtypes, and unique glial specializations. We show how several cell-specific molecular features arise in a sex-dependent manner during development. Based on the molecular data, we were also able to electrophysiologically probe, for the first time, predicted GABAergic subtypes within RA. To facilitate future utilization of the data, we have developed interactive apps that allow integration of cell level molecular data with developmental and spatial distribution data from our gene expression brain atlas (ZEBrA). With this resource, users can explore molecular specializations of vocal-motor neurons and support cells that likely reflect adaptations key to the physiology and evolution of vocal control circuits. 2 samples