The overarching theme of this K23 application is to develop a research program with the aim of improving outcomes for children with hearing loss and to further my career as a clinician-scientist. In order to develop a career as a clinician scientist, together with my mentors, we have developed a training program that includes three goals: 1) utilizing evoked potential responses to develop a biomarker of infant speech discrimination, 2) learning techniques to establish predictive validity, and 3) in-depth training i longitudinal statistical analysis. This training will be accomplished through mentorship, didactic course work, and a research project. This research project was developed due to the considerable variation in speech and language outcomes in children with hearing loss. While many gains have been made since the beginning of newborn hearing screenings, there is still significant work that needs to be done to optimally fit amplification in infants with hearing loss,to decrease the gap in listening and spoken language abilities between normal hearing and hard- of-hearing children. Behavioral techniques such as a conditioned head turn are available to assess speech discrimination in infants. These techniques, however, are limited both by a minimum age limit and by impracticality for the large group of infants with secondary disabilities. The development of a biomarker for infant speech discrimination would significantly impact the 3 out of 1000 infants per year identified with permanent hearing loss. As a first step, this application seeks to validate a biomarker of infant speech perception that can be measured shortly after the fitting of amplification. The event-related potential known as the mismatch response/negativity (MMR/N) is the proposed biomarker. Pilot data collection over the past year has allowed us to obtain reliable data in 14 normal hearing (NH) infants and two infants with hearing loss (HL). These methods need to be validated in a larger population. Further validation will be done for the stimulus type (speech and non-speech) and to assess the reliability and sensitivity of analysis type (signal averaging vs. principal component analysis) in normal hearing and hard-of-hearing infants. These children will be followed longitudinally. The same children who participated in MMR/N at 2 months will be seen again at 7 months to have their speech perception examined behaviorally using a conditioned head turn technique known as visually reinforcement infant speech discrimination (VRISD). Language outcomes will be assessed in the same children who participated in the MMR/N and VRISD protocols when they are 16, 24, 27, and 30 months. This design will allow examination of the relationship of MMR/N with behavioral speech perception and later language abilities tracked over time to determine MMR/Ns validity as a biomarker for speech perception abilities. The proposed research will advance MMR/N approaches in infants with hearing loss and determine if MMR/N can be used as a measure of speech discrimination in this population. The central hypothesis of this proposal is that a non-invasive speech-evoked auditory potential, MMR/N, can be used to determine if the amplified speech signal provides sufficient audibility for babies with hearing loss at 2 months of age to discriminate between two different speech sounds and there will be a relationship between language abilities at 16, 24, 27, and 30 months of age and MMR/N at 2 months. The research training provided by the K23 funding mechanism will allow me to widen my knowledge base in auditory evoked potentials as a model for biomarker development, learn new approaches to establishing validity between two different measures, including longitudinal follow-up, as well as develop an independent line of research. The ultimate goal of this research and training program is to prepare the PI for a career as a sustainably funded clinician-scientist who focuses on the need for translational research linking mechanisms of infant speech perception to evidence based clinical practice.
Even with the advent of universal newborn hearing screenings and the significant gains as a result of early intervention, children with hearing loss continue to exhibit delayed spoken language. Research with normal- hearing infants has demonstrated that early exposure to speech is critical to language development. Infants with hearing loss are likely to experience delays in the first year of life if hearing aids do not provie full access to spoken language. These delays are evident in spoken language abilities and may explain later challenges with literacy. However, methods of assessment do not allow us to determine whether a hearing aid fit is optimal in infants younger than 6 months of age. The research project proposed here seeks to develop a non-invasive, objective index of infant speech perception that can be used to determine if children can discriminate speech in early infancy shortly following the initial fit. The outcome of this project have the potential to influece critical habilitation decisions for infants with hearing loss and thus holds high public health relevance for the fields of Audiology, Speech/Language Pathology, Deaf Education and Otolaryngology.
| Uhler, Kristin M; Gifford, René H; Forster, Jeri E et al. (2018) Refining Stimulus Parameters in Assessing Infant Speech Perception Using Visual Reinforcement Infant Speech Discrimination in Infants with and without Hearing Loss: Presentation Level. J Am Acad Audiol 29:847-854 |
| Uhler, Kristin M; Hunter, Sharon K; Tierney, Elyse et al. (2018) The relationship between mismatch response and the acoustic change complex in normal hearing infants. Clin Neurophysiol 129:1148-1160 |
| Gilley, Phillip M; Uhler, Kristin; Watson, Kaylee et al. (2017) Spectral-temporal EEG dynamics of speech discrimination processing in infants during sleep. BMC Neurosci 18:34 |
| Uhler, Kristin M; Baca, Rosalinda; Dudas, Emily et al. (2015) Refining Stimulus Parameters in Assessing Infant Speech Perception Using Visual Reinforcement Infant Speech Discrimination: Sensation Level. J Am Acad Audiol 26:807-14 |
