Antje Ihlefeld - US grants

DESCRIPTION (provided by applicant): A major challenge for hearing-impaired listeners and cochlear implant users is to detect and understand speech in situations with background sound. Detecting a target sound in background noise is often easier when the background energy is non-stationary and fluctuates over time. Normal-hearing listeners can accomplish this feat by extracting target information during temporary reductions in background sound energy, a benefit known as modulation masking release (MMR). MMR is much reduced or absent in the hearing impaired. This proposal aims to identify behavioral and neuronal mechanisms for MMR, and examine how sound deprivation affects them. I believe that the results emanating from this proposal will considerably further our understanding of how hearing loss affects our capacity to combat masking, and help develop remediation strategies for hearing loss. Some of the difficulties facing hearing-impaired listeners stem not only from degraded sensory input but also from an altered central auditory system along the entire neuraxis. Because the effect of sound deprivation on MMR is poorly understood, a necessary first step is to explore how the detection of tones in noise is performed by a model organism of human auditory processing, the Mongolian gerbil (Meriones unguiculatus). We lack comprehensive knowledge that may link perception and neuronal activity associated with MMR. By combining empirical approaches in psychoacoustics and in-vivo physiology recordings from awake animals, my key goal is to improve our understanding on how the sound deprived central auditory system processes a challenging task such as MMR. First, I will train sound-deprived animals to detect a tone in noise backgrounds, and compare their performance to normal-hearing controls. Second, I will measure neuronal activity in core auditory cortex from these trained animals. The discharge patterns will reveal how controls detect a tone in fluctuating background sound and whether altered discharge patterns occur in CHL that correlate with hearing- loss related behavioral deficits. Collectively, this proposal will assess how sound deprivation affects MMR at both perceptual and cortical processing levels. The results are expected to significantly advance our understanding of the origins and scope of central processing deficits amongst the hearing impaired.

The broader impact/commercial potential of this I-Corps project is the development of a diagnostic device for auditory processing disorder (APD). Individuals with APD cannot communicate effectively in situations with background sound, which is debilitating. This can lead to social isolation and reduced employment opportunities. An estimated 25 million Americans suffer from APD, including veterans with traumatic brain injury. However, a substantial diagnostic challenge in audiological practice is that patients with comparable peripheral hearing often have vastly different treatment outcomes. APD could be a valuable addition to the list of candidate tests.

This I-Corps project explores translation of a screening device that delivers an APD test battery via calibrated headphones, enabling patient testing of audiometric pure tone thresholds, speech intelligibility in the presence of different types of background sound - speech or noise, in multiple languages, gap detection, and sound localization. Behavioral APD test batteries may be a highly cost-effective way to screen for APD. Moreover, the device will allow testing in multiple languages, increasing the number of eligible patients. Later, the goal is to provide an additional, proprietary score to diagnose an individual?s vulnerability to APD.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.