The role of auditory cortex in segregating sounds in individuals with normal hearing and age-related hearing loss

Listening to someone speak in a noisy room is a common problem associated with age-related hearing loss. More than 50% of people over the age of sixty suffer from some degree of hearing loss, and while both hearing aids and cochlear implants can improve hearing, in a noisy environment, hearing is still generally problematic. Being able to listen to one sound in the presence of other distracting sounds, commonly referred to as "the cocktail party problem", is fundamental to our ability to recognize speech and appreciate music. The proposed research project will investigate how the brain solves this problem, and create a model system to study what changes in the brain after age-related hearing loss, that makes it more difficult to hear someone's voice in a noisy room.

The recognition of an acoustic signal in the presence of other distracting sounds is a common problem associated with age-related hearing loss. More than 50% of people over the age of sixty suffer from some degree of hearing loss, and while both hearing aids and cochlear implants can improve hearing, sound segregation is generally still problematic. The perceptual segregation of simultaneously occurring acoustic signals, commonly referred to as "the cocktail party problem", is fundamental to our ability to recognize speech and appreciate music. While auditory cortex is believed to play an important role in the segregation of concurrent complex sounds, little is known about how this is accomplished at a neuronal level. The proposed research project will investigate how auditory cortical neurons encode and segregate multiple acoustic signals. Our proposed research project will investigate how information is encoded by coordinated neuronal activity, in the form of synchrony and co modulation of firing rate. The role of higher-level neuronal interactions for encoding information has important implications to our understanding of perceptual deficits associated with hearing-loss and the development of auditory cortical prosthetics that can correct these deficits.

The goal of our research proposal is to examine the cortical representation of sound segregation in passive listening and active listening (in both normal hearing and hearing impaired individuals). This research project has the most immediate impact on researchers studying audition, specifically the research topics of hearing loss, auditory cortical processing and sound source segregation. Outside of auditory neuroscience, the work will impact more general neuroscience research, in the areas of neural coding and object processing. In addition, we will be using a technique of chronic multi-electrode recording from the auditory cortex of freely moving mice, to record ensembles of single units during both passive and behaving conditions. Although these techniques are commonly used for studying the hippocampus, currently there are few labs that have pioneered these methods in rodent auditory cortex. We hope that by making these techniques freely-available to other researchers (and providing the opportunity to be trained in our lab), more labs will use large-scale recording methodologies in freely-moving, behaving animals to study auditory cortex.

In addition to neuroscientists, we aim to transfer knowledge gained from our experiments to ENT clinicians, hearing aid/cochlear implant technology companies. The goal of our research is to understand why sound segregation is more difficult after hearing loss, which in turn can be used to improve the current design of hearing aids and cochlear implants, and improve the quality of life for individuals with hearing loss.

Another target audience we plan to impact is the general public, where we can communicate the results of our research, and also describe some of the difficulties faced by individuals with hearing loss, including hearing someone speak in the presence of other sounds (or background noise). Improving the public's knowledge about the difficulties faced by individual with hearing loss, will help improve overall awareness of these issues.