Auditory Circuits for Interpreting Vocal Communication Signals

University Of California Berkeley, Berkeley CA

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Abstract

Project Summary/Abstract Interpreting vocalizations in communication, such as human speech, necessitates the segmentation of the sound stream into meaningful units and the identification of their corresponding meanings. Although research on the neural basis of human speech perception has demonstrated the entrainment of neural activity in auditory areas by the speech sound envelope, the specific mechanisms underlying neural segmentation and its facilitation of the identification task remain poorly understood. Furthermore, while categorical neural responses to sound classes have been observed, the computational processes and representations enabling the categorization of a complete communication system, for example, encompassing all phonemes in a human language, remain largely unexplored. To bridge these gaps in knowledge, we have developed a songbird model that promises to shed light on these fundamental processes. In previous research, we made a significant breakthrough by uncovering a combinatorial neural code in the avian auditory cortex responsible for identifying all call types within a bird's repertoire. Building upon this discovery, our study aims to investigate how the auditory system generates this ensemble code for identification while concurrently segmenting the sound stream into meaningful segments. In Aim 1, we will examine the neural basis of segmentation using animals actively engaged in listening tasks or natural communication scenarios, allowing us to study the impact of attention on this process. The human vocal communication system also relies on the ability to learn and identify novel sound categories, such as new words or the distinct voice of a speaker. Fascinatingly, our research has demonstrated that songbirds possess a similar capacity to rapidly recognize the voice characteristics of numerous conspecifics. Accomplishing this voice identity task necessitates the formation of auditory memories. In Aim 2, we will explore the neural mechanisms underlying the identification task for these learned vocal categories. Our investigations will provide valuable insights into the roles played by distinct circuits within the auditory cortex in processing semantics and voice. This knowledge is critical for comprehending how dysfunctional auditory processing in multiple mental disorders as well as aging affects speech recognition and, subsequently, other cognitive abilities.