The effects of age and sex on rates of hearing loss for pure tones varying in duration

Mice are frequently used to study and model presbycusis due to similarities in the human and mouse cochleae and in genetic makeup. Most of the previous research on presbycusis used electrophysiological measures of hearing in mice, leading to an underrepresentation of behavioral experiments in the literature on mouse aging. The goal of the current research was to fill this gap by behaviorally measuring audiograms and temporal summation functions in aging mice. Adult mice were trained and tested using an accelerated longitudinal design. Mice were trained on a detection task using operant conditioning procedures with positive reinforcement. Audiograms were constructed using thresholds for 8, 16, 24, 42, and 64 kHz pure tones. Temporal summation functions were constructed for 16 and 64 kHz pure tones ranging from 20 to 800 ms in duration. The results revealed that mice retain pure tone hearing late into their lifespan, with high-frequency hearing loss preceding low-frequency hearing loss. Mice also benefit from increases in the duration of pure tones; however. this benefit decreases with age. Generally, male mice lose hearing at a faster rate than females. These results highlight the importance of measuring hearing in awake, trained, behaving subjects when comparing presbycusis across species.