A causal relationship between hearing loss and cognitive impairment

Conclusion Moderate hearing loss in young mice caused decreases in cognition associated with spatial working and recognition memories in 6 months. These results provide evidence for a causal relationship between hearing loss and cognitive impairment. Objectives Hypothesized mechanisms to connect sensory and cognitive functions include the sensory-deprivation, information-degradation, and common-cause hypotheses. This study intended to investigate the effect of hearing loss on cognitive function, as estimated by radial arm maze (RAM) and novel object recognition (NOR) tasks in mice through age- and hearing-matched longitudinal work during a 6-month period. Methods Twenty-four male C57BL/6 mice aged 1 month with normal ABR thresholds were used. Twelve mice in the hearing loss (HL) group were exposed to white noise at 110 dB SPL for 60 min every day for 20 days. At post-noise 6 months, all mice underwent RAM and one-trial NOR test. RAM performance measures and NOR discrimination index were compared between two groups. Results At 6 months after noise exposure, all mice in the experimental group had moderate hearing loss. Most of the RAM performances improved gradually within each group across five trials, probably due to learning effect. The HL group showed lower performance scores than the control group in several trial points in the RAM task. The contact time with the novel object was shorter in the HL group than in the control group.