The Medical University of South Carolina
Neural determinants of age-related change in auditory-visual speech processing

Older adults typically have more difficulty than younger adults identifying the speech they hear, especially in noisy listening environments. However, some older adults demonstrate a preserved ability to identify speech that is both heard and seen. This preserved audiovisual speech perception by older adults is not explained by an improved ability to speechread (lipread), as speechreading also typically declines with age. Instead, older adults can exhibit an improved ability to integrate information available from across auditory and visual sources. This behavioral evidence is consistent with findings suggesting that the neural processing of audiovisual speech can improve with age. Despite the accumulating and intriguing evidence, the underlying changes in brain structure and function that support the preservation of audiovisual speech perception in older adults remains a critical knowledge gap. This project uses an innovative neural systems approach to determine how age-related changes in cortical structure and function, both within and between regions of the brain, can preserve audiovisual speech perception in older adults.

Carnegie Mellon University
Neural mechanisms of speech sound encoding in older adults

Many older adults have trouble understanding speech in noisy environments, often to a greater extent than their hearing thresholds would predict. Age-related changes in the central auditory system, not just hearing loss, are thought to contribute to this perceptual impairment, but the exact mechanisms by which this would occur are not yet known. As individuals age, auditory neurons become less able to synchronize to the timing information in sound. This project will examine the relationship between reduced neural processing of fine timing information and older adults’ ability to encode the acoustic building blocks of speech sounds. Limited capacity to code and use these acoustic cues might impair speech perception, particularly in the presence of background noise, independent of hearing thresholds. The results of this study will provide a better understanding of how the neural mechanisms important for speech-in-noise recognition may be altered with age, laying the groundwork for development of novel treatments for older adults who experience difficulty perceiving speech in noise.

The University of Chicago

Age-related disruption of calcium homeostasis in vestibular sensory cells

Falls are a major health concern for older adults, and problems with balance are one of the main reasons they occur. Our sense of balance relies on sensory cells in the inner ear, called vestibular hair cells, that detect head movements and communicate this information to the brain. As we age, some of these cells are lost, but their function may begin to change long before that. We want to understand what happens during this earlier stage, when it may still be possible to protect hair cells' function.

Our project focuses on calcium, which plays an essential role in how vestibular hair cells work. These cells need calcium to sense movement and communicate with the brain, but they also need to carefully control how much calcium is present and where it goes. We think that this control may become less effective with age, gradually interfering with the cells’ ability to provide accurate information about head movement.

To study this, we will compare young and old mice at several levels. First, we will study individual vestibular hair cells to understand how their calcium signals and electrical activity change with age. We will then use specialized imaging methods to directly observe calcium activity in many hair cells at the same time. This will allow us to see how strongly the cells respond to a given mechanical stimulus and how well their responses are synchronized across the population. Finally, we will use behavioral tests of balance to examine whether changes in hair cell function are associated with impaired vestibular function in older mice.

By finding out what starts to go wrong in vestibular hair cells as they age, we hope to better understand why balance declines in older adults. In the long term, this knowledge could help identify ways to protect the inner ear and prevent or reduce age-related balance problems.