PROJECT SUMMARY Infants who are hard-of-hearing (IHH) are at significantly increased risk for poor auditory development and speech perception (e.g., perceiving cat versus hat), despite early hearing detection and intervention. For infants with normal hearing (INH), the first year of life is a seminal period for refining speech perception abilities shaped by exposure to language. During this early developmental period, perceptual skills become more narrowly tuned to spectral and temporal features, or cues, that favor discrimination of behaviorally relevant information. Thus, early perceptual skill development is driven by the dynamic interplay between language experiences and the concurrent maturation of auditory sensory pathways. Because refinement of speech discrimination abilities depends on an infant's exposure to speech sounds, IHH are susceptible to atypical development during this period. What remains poorly understood is the impact of inconsistent auditory cue access and poor speech perception among IHH. There is a critical need to map auditory development among IHH and to understand the long-term impacts of auditory cue processing on speech perception abilities. Filling this need will lay the foundation for developing clinical tools that will aid in personalization of intervention strategies. Our overall objectives in this application are to 1) map the emergence of speech perception among IHH compared to a cohort of age-matched INH; 2) describe the effects of auditory speech cue access on speech discrimination in noise, and 3) to assess the relationship between attunement of speech perception and functional auditory skills. By comparing these groups at 3, 6, and 12 months of age, we can describe the extent to which maturation and experience contribute to the emergence and attunement of speech perception abilities. To document speech perception development, we will use scalp-recorded electroencephalography (EEG) measured in response to native and non-native speech sounds. Our hypotheses are: 1) INH will demonstrate attunement for vowel and consonant speech sounds, but IHH will not; 2) speech perception abilities measured at 12 months of age will be positively correlated with discrimination abilities; and 3) auditory development scores will be higher for infants who demonstrate attunement to English consonant sounds. Results will inform our understanding of speech perception and auditory skill development among IHH. Our long-term goal is to improve speech and language outcomes in children with hearing loss. This project is relevant to NIDCD's mission of understanding the mechanisms of hearing loss which impact the emergence of speech perception and functional auditory skill development.