Cell Survival in a Neural Circuit for Learning

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Like humans, juvenile songbirds learn to imitate the vocal patterns of an adult during a sensitive period of development. Also like humans, songbird vocal patterns are controlled by a forebrain network that includes pre-motor, striatal, and auditory pathways for processing vocal sounds and gestures. This proposal seeks to understand how these pathways interact to produce stable vocal patterns. Our working hypothesis states that learned song results from an integration of pre-motor and striatal pathways encoding stereotyped and variable vocal patterns, respectively. This simple hypothesis makes clear predictions about the vocal effects of altering the relative strength of pre-motor and striatal pathways. For example, we have shown that weakening the premotor pathway in adult birds (via partial ablation) produces highly variable singing reminiscent of a learning juvenile. However, adult vocal patterns show surprising resilience as birds subsequently recover stable song within 1 week. This recovery depends on auditory feedback, indicating that adult vocal recovery involves instructive mechanisms similar to those that guide juvenile learning. Recently, we designed an experiment to identify the neural locus of these instructive mechanisms in adult birds and demonstrated that they cannot lie within their long-presumed location - the striatal pathway. Here, we propose experiments to 1.) test our model of pre-motor and striatal pathway function in juvenile birds and 2.) identify the neural loci and mechanisms by which auditory feedback promotes vocal learning (in juveniles) and maintenance of stable song (in adults). These experiments will provide new information about the functional architecture of the songbird vocal control network - this knowledge will offer new insight into the functional architecture of the analogous neural regions that control human vocal learning. 1