The Mouse Auditory Testing (MAT) Core assists investigators at the National Institute on Deafness and Other Communication Disorders (NIDCD) and their collaborators with tests of auditory and vestibular function in mice. Two physiological measures of auditory function are employed in the MAT Core: the auditory brainstem response (ABR) and distortion-product otoacoustic emissions (DPOAEs). The ABR is an evoked potential that can be used to estimate hearing thresholds. DPOAEs are soft sounds that are recorded in the ear canal using a small microphone. DPOAEs can be used to screen for hearing loss and to evaluate inner ear function; specifically, the presence of DPOAEs indicates normal function of outer hair cells in the inner ear. Vestibular sensory evoked potentials (VsEPs) are measured to assess vestibular function. VsEPs are generated by the vestibular nervous system in response to linear movements of the head and provide information about function of the otolith organs (utricle and saccule). Dr. Fitzgerald trained three NIDCD investigators in auditory function testing and provided orientation to the Core for three members of the Hertzano lab. Two investigators began training in vestibular evoked testing with Dr. Wafa. Eleven NIDCD investigators conducted auditory function testing independently with support from the MAT Core. Dr. Fitzgerald trained one post-doctoral fellow from Dr. Arun’s lab in the Blast Induced Neurotrauma Branch (BINT), Center for Military Psychiatry and Neuroscience (CMPN) at the Walter Reed Army Institute of Research (WRAIR) in DPOAE and ABR data analyses and interpretation. In July 2024, the MAT Core participated in the annual Earssentials workshop, a week-long course designed to expose new trainees and interested scientists to auditory research at the NIDCD through lectures and laboratory exercises. Trainees participated in a laboratory training exercise on auditory and vestibular testing in mice given by Dr. Fitzgerald, Dr. Wafa, Elizabeth Wilson Bernhard, and Dr. Katharine Fernandez. Core staff collaborated on and/or supported projects conducted in eight NIDCD labs: Section on Sensory Physiology and Biophysics (PI: Angela Ballesteros, Ph.D.) MAT Core staff collaborated with Dr. Emdad Rahman, Runjia Cui, and Dr. Ballesteros to examine auditory and vestibular function in a mutant mouse. Inner Ear Gene Therapy Program (PI: Wade Chien, M.D.) Dr. Fitzgerald trained Dr. Michelle Suh and Keith Abbey in auditory testing. Dr. Wafa trained Kevin Isgrig in vestibular testing. The Core supported auditory testing by Kevin Isgrig, Dr. Yasuko Ishibashi, Jianliang Zhu, and Zarek Fasoranti for multiple projects investigating the use of gene therapy to remediate hearing loss or vestibular dysfunction. Section on Sensory Cell Biology (PI: Lisa Cunningham, Ph.D.) The Core supported auditory testing by Drs. Cathy Sung and John Lee for projects investigating the mechanisms behind and prevention of hearing loss caused by ototoxic medications. Laboratory of Molecular Genetics (PI: Thomas Friedman, Ph.D.) Core staff collaborated on multiple projects examining auditory function in various mutant mouse strains, including projects with Dr. Inna Belyantseva, Dr. Sayaka Inagaki, Dr. Rabia Faridi, and Elizabeth Wilson Bernhard, and on a collaboration between the Chien lab and Dr. Belyantseva. Drs. Fitzgerald and Wafa collaborated with Kerstin Valente and Dr. Isabelle Roux on projects that included auditory and vestibular function testing in several mouse lines segregating alleles of Slc26a4 with missense mutations identified in patients with hearing loss and enlarged vestibular aqueduct. Auditory Development and Restoration Program (PI: Michael Hoa, M.D.) The Core supported auditory testing by Rafal Olszewski on a mouse model of fluctuating hearing loss. Section on Structural Cell Biology (PI: Bechara Kachar, M.D.) MAT Core staff collaborated with Drs. Wonchul Shin and Kachar on a project examining auditory and vestibular function in a mutant mouse. Laboratory of Cochlear Development (PI: Matthew Kelley, Ph.D.) The Core supported auditory testing of mutant mice for three projects by Dr. Braulio Peguero and two projects by Dr. Susumu Sakamoto. Section on Sensory Cell Regeneration and Development (PI: Doris Wu, Ph.D.) MAT Core staff collaborated with Drs. Youngrae Ji, So Young Kim, Hyunjae Lee, and Dr. Wu on three projects examining vestibular function in multiple mutant mouse strains. Dr. Wafa began training Dr. Hyunjae Lee in vestibular testing. Dr. Fitzgerald and Ms. Krasnopolsky collaborated with Drs. Lok Sum Wong (Otomagnetics) and Wu on a project examining auditory function in a mutant mouse.