PROJECT SUMMARY/ABSTRACT In species that learn vocalizations, social experience acts on genetically encoded forebrain circuits to enable vocal imitation. Critical periods limit when this social experience can influence the development and function of neural circuits required for vocal learning. In songbirds, HVC is a necessary song neurocircuit component to form a song memory from the social experience of hearing an adult vocal model (“tutoring”). Yet, HVC is also necessary as a premotor region after the critical period. It is not well understood how the tutoring experience acts on HVC to allow this dual sensory and motor function. Our single-nucleus RNA-sequencing results demonstrate that the proportion of HVC’s projection neurons change throughout development. During the sensory critical period, HVC neurons that project to the auditory region and basal ganglia pathway are proportionally more than those that project to the motor pathway. I hypothesize that HVC uses these distinct cell types to function as a sensory region early in development prior to the maturation of its motor function. I therefore expect that the two former projection neuron types experience the most genetic and electrophysiological changes related to learning from the social tutoring experience compared to the latter projection neuron type. To test this, I will examine single-cell epigenomic and transcriptional changes from tutoring experience to measure changes in immediate early genes and genes related to plasticity and learning. I will also use optogenetic circuit mapping to measure the changes in synaptic strength from tutoring experience.