Noise-induced hearing loss reduces inhibitory neurotransmitter synthesis in ventral hippocampus and contributes to the social memory deficits of mice.

Despite affecting over 1.5 billion people globally, hearing loss (HL) has been referred to as an "invisible disability", with noise exposure being a major causative factor. Accumulating evidence suggests that HL can induce cognitive impairment. However, relatively little is known about the effects of noise-induced hearing loss (NIHL) on social memory. This study aimed to further investigate the effect of NIHL on social behaviours in mice. We established a rodent model of NIHL using 4-week-old C57BL/6J mice who experienced narrow noise exposure at 116 dB for 3 h per day over two consecutive days. Hearing ability was subsequently evaluated through auditory brainstem response (ABR) testing, and potential changes in the morphology of cochlear hair cells were assessed using immunofluorescence. The sociability and social memory of the mice were evaluated using the three-chamber social interaction test. Noise exposure resulted in complete and persistent HL in C57BL/6J mice, accompanied by severe loss of cochlear hair cells. More importantly, social memory was impaired in adult NIHL mice, whereas their sociability remained intact, these changes were accompanied by a decrease in the protein levels of the inhibitory neuron marker glutamic acid decarboxylase 67 (GAD67) in the ventral hippocampus. This study is the first to confirm that long-term auditory deprivation from HL induced by noise exposure results in social memory deficits in mice without altering their sociability.