PROJECT SUMMARY/ABSTRACT The ability of patients with cochlear-implants (CI) to discriminate speech sounds is the fundamental measure of efficacy that clinicians use to create personalized clinical interventions. Given the universal importance of early identification and treatment for children born with hearing loss, the most appropriate clinical intervention for children with CIs should be initiated at the earliest possible age. Despite the routine implantation of prelingually-deaf infants as young as 9-months-old, there are currently no established clinical measures of CI efficacy for children younger than approximately 4-years-old. The long-term goal of the proposed research is to develop new measures of device efficacy in cochlear-implanted infants that can be used to drive clinical decisions at a much earlier age than is currently possible. The ability to perceive patterns of temporal or spectral intensity modulation in a noise, or “acoustic modulation perception”, is known to predict speech understanding in adult CI users. In previous work, the PI adapted tests of acoustic modulation perception for testing infants and young children. The next step, proposed in this application, will be to investigate how acoustic modulation perception develops, and relates to speech perception, in implanted infants. This will involve examining the development of two independent factors with markedly different trajectories: the ability to resolve the spectral place or timing of modulation, and sensitivity to intensity modulation across frequency or time. The central hypothesis is that both normal hearing and implanted infants will show an asymmetry in development of these factors. Frequency and temporal resolution is expected to mature by 6-months postnatal hearing-age whereas sensitivity to intensity modulation is expected to remain immature through 7-10 years old. The basis for this hypothesis is that frequency and temporal resolution reflect early-developing peripheral auditory mechanisms whereas sensitivity to intensity modulation reflects later-developing central auditory mechanisms. There are 3 specific aims to this proposal. The first is to characterize the developmental trajectory for frequency and temporal resolution in implanted and normal hearing infants during the first 6 months of post- natal hearing experience. The second is to compare the developmental trajectory of spectral and temporal modulation sensitivity in children implanted during infancy with that of normal hearing children through 10- years-of-age. The third is to determine if frequency and temporal resolution independently predict speech perception outcomes in implanted children. This work is a necessary step toward the goal of developing age- appropriate, nonlinguistic measures of acoustic modulation perception that reflect CI efficacy in implanted infants. If the long-term goal of the proposed research is realized, the positive impact will be to enable earlier, more effective, ...