Auditory cortical tuning to communication sounds and genetic constraints on the vocal learning landscape

Project Summary Hearing and speech are fundamental to human communication. Before infants are 12 months old, they have learned the statistical regularities of speech sounds around them, which guides vocal learning throughout early life and permanently alters auditory coding in cortical neurons. Deficits in cortical speech coding are hallmarks of central auditory disorders such as auditory processing disorder (APD), specific language impairment (SLI), and autism spectrum disorder (ASD), which together affect an estimated 7% of children. These disorders are highly heritable and involve additive effects of multiple gene mutations. But, how genes constrain the landscape through which auditory coding unfolds over development is entirely unknown. The proposed aims test specific hypotheses regarding genetic constraints on auditory coding in songbirds, an animal model of speech processing. Like humans and unlike other animals, songbirds learn to sing by learning regularities in the vocal sounds of adults they interact with socially, and auditory cortical coding is permanently altered by experience. The songbird secondary auditory cortex, caudomedial nidopallium (NCM) is required for vocal learning, and contains neurons that are selectively tuned for acoustics of songs heard in early life. Preliminary behavioral data indicate that juveniles raised by birds of a different species learn the morphologic structure of their foster father’s song, but arrange their song with temporal structure typical of their genetic relatives, despite never having heard those songs. In contrast, hybrid birds born of mixed-species parents copy both the morphology and temporal structure of their father’s song, despite having only half the genetic makeup. These data lead me to hypothesize that separate subpopulations of NCM neurons selectively code for song morphology and temporal structure (Aim 1), and that temporal coding is constrained by genetics (Aim 2). I propose to analyze singing behavior in songbirds with differing genetic backgrounds and specific differences in singing behavior. I will compare electrophysiological responses of their NCM neurons to natural songs, songs with altered temporal structure, and synthetic sounds that systematically vary in acoustics and timing. I will use neural encoding analyses to measure which stimulus features drive responses, and decoding analyses to measure what information neurons carry about stimuli. Expected outcomes will provide fundamental insights into the genetic sources of limitations on cortical auditory coding capacity, and will inform mechanism-based approaches to treating central auditory disorders such as APD, SLI, and ASD. The training plan includes training in electrophysiology in awake animals, advanced neural data analyses, developing expertise in behavioral genetics, and writing for journal publications, grants, and conference presentations. Training will take place in the sponsor’s and co-sponsor’s labs, housed in Columbia University’s Zuckerman Institute. The Institute is home to world-renowned neuroscientists and state-of-the-art facilities.