Spectro-temporal interactions in electric and acoustic auditory perception

About This Grant

PROJECT SUMMARY Although hearing aids and cochlear implants (CIs) improve the ability of people with sensorineural hearing loss (SNHL) to communicate, performance remains stubbornly low, particularly in noisy backgrounds. This is a critical health issue, not least because of the strong association between hearing abilities and cognitive decline with age. Older adults, even those with typical hearing (TH), also experience deficits understanding speech in noise in ways that remain poorly understood. Our long-term goal is to uncover the mechanisms that limit auditory and speech perception under challenging acoustic conditions in adults with and without hearing loss across the lifespan. This goal is addressed under three specific aims that explore interlinked aspects of the spectro-temporal encoding of auditory and speech sounds. Under Aim 1, the fundamental mechanisms that allow us to detect and identify speech and non-speech sounds in noise are explored. A new hypothesis involving the processing of amplitude fluctuations across frequency is compared with the classic hypothesis involving the processing of energy changes across frequency. Empirical results in adults with SNHL, CIs, and TH across the lifespan will be compared with predictions from state-of-the-art computational models of the auditory periphery and midbrain. Under Aim 2, the relative contributions of peripheral and more central factors to deficits in speech perception in noise with hearing loss and age are studied using a novel intervention approach, rather than more traditional correlational methods. By manipulating the degree of peripheral spectral resolution and temporal fine structure cues available in the speech sounds themselves, the experiments test the hypothesis that the bulk of age effects for speech in noise can be accounted for by changes in peripheral representations. Under Aim 3, auditory and speech perception is studied with respect to the influence of spectral contrast and context effects. Perception is critically dependent on the surrounding context in which the sensory signals are received, but we know little about how these dependencies are altered by either age or hearing loss. The implication is that any changes in our ability to make use of sensory context may be impacted by sensory loss or age in ways that are not detected by standard clinical tests. Our experiments will provide both behavioral and neurophysiological measures of auditory and speech context effects in TH and SNHL across the adult lifespan to test the hypothesis that changes in peripheral processing with hearing loss and age can radically affect how our perception adjusts to the surrounding context, and therefore contributes to the unexplained difficulties in communication faced by older people with and without hearing loss in dynamic acoustic environments. Overall, the results of this project will shed new light on critical perceptual issues surrounding speech understanding in challenging acoustic environments and will contribute to developing new approaches to the diagnosis, treatment, and management of hearing loss.