Auditory Information Processing in the Amygdala

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DESCRIPTION (provided by applicant): The long-term goal of this work is to improve the understanding of neural mechanisms that underlie acoustic communication. This project focuses on the amygdala, a structure known for its role in auditory fear conditioning. For this role, it receives auditory input from the thalamus and cortex, contributes to identifying a stimulu as aversive, and provides for appropriate emotional responses (e.g., autonomic responses, freezing). Recent work demonstrates a broader role for the amygdala in auditory behavior, including acoustic communication. This work is based on the view that the amygdala plays a critical role in acoustic communication through participation in several processes. 1) The amygdala "decides" whether a vocal signal is salient and whether that salience is positive or negative, based on contextual information from the vocal sequence, other sensory information, and the animal's internal state, 2) It orchestrates emotional responses that are appropriate for the received vocal communication signals and their context, 3) It modulates responsiveness to subsequent vocal signals through its direct and indirect projections to cortical and other auditory structures. In other words, the amygdala is likely to influence how we hear and respond to vocal communication signals. Understanding how the amygdala contributes to acoustic communication has been limited by lack of information on how amygdalar neurons respond to communication signals. Do amygdalar neurons discriminate among social vocalizations? What features of the auditory-evoked spike trains signal discrimination? How does contextual information modify the discrimination and discharge pattern of amygdalar neurons in response to social vocalizations? These questions are addressed within three Specific Aims that investigate the dependence of auditory responses on several forms of stimulus context: acoustic context (the sequencing of composition of vocalizations) (Aims1), other sensory context (Aim 2), and internal state (Aim 3). Auditory responses are obtained using chronic recording from the amygdala of awake, unrestrained animals in most experiments. Two animal models, big brown bats and CBA/CaJ mice, each provide particular advantages for the proposed studies. Dysfunction in the amygdala may play a critical role in abnormal relationships between acoustic inputs and emotional responses in disorders such as autism, schizophrenia, post-traumatic stress, and tinnitus. This work lays groundwork for study of the function of the amygdala in animal models of these disorders. PUBLIC HEALTH RELEVANCE: Dysfunction in the amygdala may play a critical role in the abnormal emotional responses to speech and other sounds that occurs in autism, schizophrenia, post-traumatic stress, and tinnitus. This work will establish how amygdalar neurons normally function in response to speech-like sounds, laying groundwork for study of the function of the amygdala in animal models of these disorders. !