Mechanisms of context: modulatory feedback to the auditory system

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For most social animals, vocal communication is heavily influenced by the context in which it occurs. The calls that animals produce, as well as the ways they respond to calls produced by others, depend on an individual's immediate social environment. The set of studies will explore the ability of the neuromodulator, serotonin, to signal context within auditory brain regions, allowing the auditory system to respond to calls in context-appropriate ways. The role of auditory neuron serotonin will be addressed in laboratory mice, which produce a rich repertoire of context-dependent calls. The studies will address 1) how serotonin reflects different features of the social context within auditory regions of the brain, 2) how serotonin alters the responses of auditory neurons to calls and 3) how changes in serotonin influence behavioral responses of mice to context-dependent calls. Because the auditory brain region that will be studied and the presence of serotonin in this region are conserved across a range of vertebrate species, these studies will illustrate basic principles of how the brain uses information about context. These studies will also emphasize the active role that sensory systems play in social decision-making. In conjunction with these studies, this award will support the development of an online educational unit for K-12 students: 'Decoding the secret language of mice'. The goal of this project is for students to develop hypotheses on the functions of mouse vocal signals and test them through curated audio and video files. For most social animals, producing and responding to communication vocalizations is heavily dependent on the social context. There is growing evidence that sensory systems are sensitive to social context, but how social brain regions collaborate with sensory systems to represent contextual information is not well understood. The studies will test the model that higher social regions instruct the auditory system on social context in part through the serotonergic system. The studies will be accomplished in laboratory mice, which have a rich repertoire of context-dependent vocal signals and responses that are influenced by acute events, prior experience, and internal state. Experiments will focus on the inferior colliculus (IC), a conserved auditory bottleneck important to a number of acoustically driven behaviors. Three main objectives will address 1) how serotonin reflects different features of the social context within auditory regions of the brain, 2) how serotonin alters the responses of auditory neurons to vocalizations and 3) how changes in serotonin influence behavioral responses of mice to context-dependent calls. These objectives will rely on a recently developed behavioral paradigm in which male mice respond to female squeaks with the suppression of courtship vocalizations. These studies will provide novel information on how social brain regions instruct sensory systems, and additionally focus on the role of sensory brain regions in social decision-making. An outreach project associated with these studies will develop hypothesis-testing skills in junior high- and high school students using curated audio and video files of socially interacting mice.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.