Samira Anderson, R21 Title of Project: Age-related changes in neural encoding and perception of temporal speech cues Older adults often report that they have trouble with clarity rather than loudness when conversing with others. This lack of clarity may stem from decreased ability to process the temporal cues that help to distinguish one word from another. Temporal cues, such as silent interval, consonant transition, and vowel duration may play a role in age-related deficits in speech perception. During my years as a practicing clinician, I became increasingly aware of the limitations of our current assessment and management protocols for identifying and addressing the specific age-related changes that contribute to poor speech perception. My experiences inspired me to pursue research that examines auditory impairments that may not be revealed with typical audiometric measures that focus on middle ear and cochlear function. My long-term goal is to establish an independent research career in identifying the neural mechanisms that contribute to age-related impairments in speech perception in order to better inform assessment and management protocols in clinical settings. The objectives in this particular application are to investigate the age-related changes in temporal coding underlying phoneme identification based on silent interval, consonant transition, and vowel durations, and to determine how well neural representation of these cues in the midbrain can predict behavioral performance. My central hypothesis is that age-related speech perceptual deficits arise, in part, from reduced subcortical (midbrain) encoding of duration cues in speech. The rationale for the proposed research is that improved understanding of the neural encoding deficits that contribute to impaired perception will lead to new diagnostic techniques that consider auditory function beyond the cochlea, especially in light of recent evidence of noise- and age-related changes in temporal processing. Guided by preliminary data, the hypothesis will be tested by pursuing three specific aims in younger (ages 18 to 30) and older adults (ages 55 to 70) with clinically normal audiometric thresholds: 1) to quantify aging effects on the subcortical representation and perception of within-word silent interval duration, 2) to quantify aging effects on the subcortical representation and perception of consonant transition duration, and 3) to quantify aging effects on the subcortical representation and perception of vowel duration. Under these aims, phoneme identification functions will be obtained for words that differ along continua of silent interval, consonant transition, and vowel durations, and frequency following responses will be recorded to the endpoints of these continua. The approach is innovative because both psychophysical and electrophysiological measures of naturally produced words will be obtained to determine contributing factors in older listeners' auditory temporal deficits. The proposed research is significant, because the results of the study will provide a scientific basis for improving diagnostic assessment of auditory function and for targeting specific temporal processing deficits in hearing aid algorithms and training programs.