Binaural Spectral and Temporal Integration with Hearing Loss and Hearing Devices - Project Summary Approximately 38 million Americans have a hearing impairment. While hearing devices such as hearing aids (HAs) and cochlear implants (CIs) are successful in improving speech recognition for many hearing- impaired individuals, there is still significant variability in benefit, and speech recognition in noise remains a problem. One factor that may limit benefit, especially binaural benefit, is abnormal binaural integration of both spectral and temporal information. A prerequisite for binaural integration is binaural fusion — the fusion of stimuli from the two ears into a single auditory object. Unlike normal-hearing (NH) listeners, we have shown that many HA and CI users experience abnormally “broad” binaural fusion in the spectral domain, such that pitches that differ greatly in frequency between the two ears are still heard as a single percept. Individuals with broad fusion also experience abnormal binaural spectral integration - averaging and thus distortion of spectral information across the ears when disparate sounds are fused. Broad fusion has been shown to be associated with binaural interference — poorer speech recognition with two ears compared to one. Most importantly, we demonstrated recently that broad fusion is associated with greater difficulty with understanding speech in challenging multi-talker listening situations, such as noisy restaurants. Difficulties with speech understanding in noise is a major complaint of both HA and CI users. These results demonstrate the high clinical significance of abnormal binaural fusion for the difficulties that listeners with hearing loss and hearing devices experience with speech perception in background noise. However, some gaps remain in our understanding of binaural fusion, especially in individuals with hearing loss. Do HA and CI users also differ from NH listeners in binaural fusion in the temporal domain, and if so, how does this affect speech recognition? Another major gap is in how to treat abnormal binaural fusion. There is unexplored potential for top-down and multi-sensory cues to be used as supplementary cues to help reduce abnormally broad binaural fusion. Thus, the goal of this proposal is to address these gaps in our understanding of: 1) how listeners with hearing loss differ from NH listeners in binaural fusion of temporal and spectro-temporal information (Aim 1), and 2) whether top-down and vibrotactile cues can sharpen binaural fusion, with potential application for rehabilitation (Aim 2). The findings will provide broader insights into the neural mechanisms underlying binaural fusion, and establish a framework for future treatments to sharpen binaural fusion to maximize binaural benefits and improve speech perception in noise.
