Grant: Discovery Grants Program - Individual

Speech is the hallmark of human communication, but we do not have a complete understanding of how the auditory system processes speech sounds. In humans, we can study physiological evidence of auditory processing by measuring auditory evoked potentials (EPs) using electrodes placed on the scalp. EPs show changes in neural activity that take place at the short time scale of speech itself. The envelope following response (EFR) is an EP generated by neural activity that is phase-locked to the periodicity of the stimulus envelope and can be elicited by speech sounds like vowels. However, the EFR is sometimes small or undetectable in normal hearing individuals. We must improve our understanding of how brain activity from different neural populations contributes to the measured signal and what the EFR can therefore tell us about speech processing. The proposed research program will investigate the mechanics of EFR generation to maximize its utility as an accessible, non-invasive, and well understood tool for investigating human auditory processing of speech sounds. The proposed research program will determine how to best measure EFRs elicited by vowels. We will also learn how vowels are coded differently from one another, and how the details of speech sounds affect the brain's activity. The use of naturally produced and subtly manipulated natural speech is much needed in auditory research due to the mismatch between the importance of speech and the predominant history of using clicks, noises, and tone-bursts in the literature. The proposed research program is important as both a basic science investigation and for practical applications. Its findings will contribute to our understanding of what EPs can tell us about the neural processing of vowels and will develop a valuable tool for future research. Auditory processing is not only directly important to communication, but also plays a central role in language learning and maintenance of speech production. The findings will be important to the speech and hearing research communities and for practical applications where speech is involved. The design and fitting procedures used for cochlear implant technology will benefit from an improved understanding of the brain's representation of speech. Methods for transmitting speech over telephones and the Internet would also benefit from an improved understanding of speech processing in the brain. We will improve our ability to address these practical applications by advancing our knowledge of the EPs available for probing the brain's response to speech.