The molecular basis for developmental sensory learning
Similar to humans, songbirds learn meaningful vocalizations from an adult tutor most effectively during a sensitive period of development. While advancements have been made in understanding the motor control of vocal production, the neural mechanisms for the sensory memories that precede and direct vocal structure are mostly undefined. In songbirds like the zebra finch, the forebrain auditory lobule (AL), the functional homologue of mammalian primary and secondary auditory cortices, is involved in adult song recognition and holds a trace of the tutor song heard during juvenile life. Thus, it may be that AL is required for developmental sensory tutor song learning. Further, gene expression studies demonstrate that genes only induced in learning-related contexts in adult songbirds are constitutively expressed in AL during the sensory phase of developmental song learning. Therefore, the hypothesis was that AL, and developmentally and experientially regulated gene expression in AL, are necessary for optimal sensory song learning during development. To test this hypothesis, three studies were designed to (1) behaviorally test that AL and molecular processes within AL are required for tutor song memorization, (2) silence individual genes in AL to test their function in developmental sensory song learning, and (3) identify and confirm a suite of genes that may shape the AL for optimal sensory learning. These studies form a comprehensive and cohesive investigation of the molecular events underlying the sensory song learning that is the foundation for song vocalizations. The zebra finch is a very useful model for these studies because some sensory song learning occurs before vocalization begins, allowing the dissection of sensory from motor and sensorimotor components of developmental song learning. The function of AL and many genes are evolutionarily conserved, thus results of these experiments have application not only to songbird researchers but also those interested in human language acquisition. >The ability to communicate is fundamental, and most people use vocal communication to navigate through their complex social lives. Vocal learning is most efficient during early life, progresses similarly to how birds learn song, and both people and birds rely primarily upon sensory processing of the vocalizations they hear to shape their own vocalizations. Thus, the study of sensory learning of tutor song in songbirds provides important insights into auditory mechanisms underlying human language acquisition.