Neuroimaging of Age-Related Changes in Speech Recognition

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Age-related declines in hearing and speech recognition are growing public health concerns that have a profound impact on the ability to communicate. Older adults describe speech recognition as fatiguing and experience speech recognition declines even after accounting for audibility, suggesting that central nervous system (CNS) declines affect speech recognition. The neuroimaging experiments proposed in Project 2 examine effects of presbyacusis and aging on central auditory and attention systems that support speech recognition. Aim 2.1 uses novel structural imaging to test the hypothesis that unique patterns of brain structure occur with unique audiometric patterns of presbyacusis. This aim is designed to characterize the extent to which 1) high frequency hearing loss occurs with trans-synaptic degeneration that stems from sensory hair cell loss, while 2) low frequency hearing loss occurs with vascular disease that is hypothesized to underlie metabolic presbyacusis. Aim 2.2 involves functional imaging and manipulations of attention systems to test the hypothesis that attention-related systems support speech recognition in older adults with hearing loss. This aim is designed to provide a mechanistic explanation for why word recognition can be better or worse than expected for hearing loss based on the engagement of specific attention systems. Aim 2.3 involves structural and functional imaging to test the hypothesis that longitudinal speech recognition changes occur with additive structural declines in auditory and attention-related cortex. This aim is designed to identify neural systems exhibiting changes that track with declines in speech recognition during a time period when auditory thresholds are relatively stable. Thus, Project 2 characterizes the unique impacts of declines in auditory thresholds and age on speech recognition, is an extension of Project 1's focus on age related changes in the auditory periphery, and will provide in vivo evidence to support mechanisms for hearing loss that are studied in Projects 3 and 4. Our overarching goal is to characterize 1) CNS declines in older adults that negatively affect speech recognition and 2) preserved structure and function that support speech recognition, thereby guiding efforts to improve communication and enhance the quality of life for older adults.