To interpret the vocalizations used in communication, such as human speech, animals and humans must perform a range of auditory tasks: the detection and localization of sounds, the perception of pitch and timbre, and the parsing and categorization of the information bearing sound features that is required for the interpretation of communication calls. Auditory neuroscientists have obtained a relatively good model of how complex sounds are represented in the primary auditory cortex primarily in terms of their spectro-temporal features. We also know that a network of higher-level auditory and associative cortical areas is involved in processing speech in humans and communication calls in animals. However, the neural circuits and the corresponding non-linear transformations that occur between primary auditory cortical areas and cortical regions that categorize communication sounds in terms of their meaning remains unknown. We are developing the avian model system to bridge this gap. Songbirds have a large repertoire of communication sounds that are used in distinct behavioral contexts. By combining behavioral and neurophysiological experiments, we will investigate how calls are categorized into call-types (semantics). We will also investigate the neural representation for learned categories that correspond to different vocalizers (voice). Using state-of-the-art computational approaches, we will decipher the sequence of non-linear processing steps occurring both at the level of single neurons and neuronal ensembles that perform these sound- to-meaning transformations. Our studies will elucidate the roles of different circuits within auditory cortex for processing semantics and voice. This knowledge will be essential to understand how dysfunctional auditory processing in certain mental disorders affects speech recognition and consequently other cognitive skills. Our work could also be instrumental in the development of novel signal processing methods for auditory neural prosthetics or hearing aids.
The purpose of this research is to discover how neural circuits in the auditory cortex perform the sound to meaning transformation for the sounds used in vocal communication. This research will be useful for designing the next generation of hearing aids and cochlear implants and will allow us to understand the causes of some learning disabilities and mental disorders that involve high-level auditory processing, including deficits in speech comprehension and other cognitive abilities.