Pathophysiology of hearing loss and its effect on cognitive function

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K18263
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 56050:Otorhinolaryngology-related
• Research Institution: National Defense Medical College
• Principal Investigator: Kurioka Takaomi 防衛医科大学校(医学教育部医学科進学課程及び専門課程、動物実験施設、共同利用研究施設、病院並びに防衛, 耳鼻咽喉科学, 講師 (30842728)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 聴覚障害 / シナプス / 難聴 / 耳鳴

Outline of Final Research Achievements

In this study, we investigated whether a decrease in sound level could induce impairment of hippocampal neurogenesis and examined the differences between unilateral conductive (uCHL) and bilateral CHL (bCHL).
Although hearing thresholds were significantly increased following CHL, CHL mice exhibited no significant loss of spiral ganglion or hippocampal neurons. Hippocampal neurogenesis was significantly and equally decreased in both sides following uCHL. More severe decreases in hippocampal neurogenesis were observed in both sides in bCHL mice compared with that in uCHL mice. Furthermore, microglial invasion significantly increased following CHL. Serum cortisol levels, which indicate stress response, significantly increased following bCHL. Therefore, auditory deprivation could lead to increased microglial invasion

Free Research Field

内耳生理学

Academic Significance and Societal Importance of the Research Achievements

伝音難聴による中耳から内耳への音響刺激の減少が蝸牛神経、脳に及ぼす影響と神経可塑性について検討した。耳栓により有意な聴力閾値の上昇を認めたが，耳栓解除後には聴力閾値は完全に回復した。組織学的には，有毛細胞や蝸牛神経の消失は認めなかったが，内有毛細胞と蝸牛神経の接合部シナプス数，蝸牛神経軸索径および髄鞘化が有意に低値となった。これらの組織学的変化は伝音難聴の解消により回復を示した。さらに海馬の神経新生能も低下を示した。以上のことから，聴覚刺激に依存して脳は可塑性を有すると考えられ，伝音難聴においても蝸牛神経への電気刺激を維持することが重要と考える。