Radial Maze Test in a Mouse Model of Noise-Induced Hearing Loss / 대한이비인후과학회지

ABSTRACT

BACKGROUND AND OBJECTIVES: Hearing loss has been hypothesized to contribute to cognitive decline in the elderly. However, earlier studies yielded conflicting results, and the causal relationship has not been elucidated to date. In the present study, the authors set up a radial maze apparatus for assessment of cognition in mice, and investigated the relationship between cognition and hearing loss that occur immediately after noise exposure. MATERIALS AND METHOD: Spatial learning and memory were assessed in male C57BL/6 mice with or without hearing loss using an unconfined, partially-baited, 8-arm radial maze with different arm length (25 or 50 cm). The performance indicators included total trial time, latency, reference memory error, working memory error, and correct entry ratio. Mice in the hearing loss group were exposed to 60 min of 110 dB white noise for 14 days, and then auditory brainstem response thresholds were measured. RESULTS: Mice showed better performances in a 25 cm-arm radial maze than in a 50 cm-arm maze. The control and the hearing loss groups exhibited similar performance curves, except for the working memory curve in 25 cm-arm radial maze. Hearing-impaired mice were better at working memory tasks than the control mice, probably due to an early cognitive compensatory mechanism. CONCLUSION: A radial maze with 25 cm arm is appropriate for the test of learning and memory in mice. Acute hearing loss after noise exposure was not associated with decreased cognition. Further follow-up research has been planned to find the effect of long-term hearing loss on cognition and the mechanism by which these two domains are connected.