Conductive Hearing Loss Aggravates Memory Decline in Alzheimer Model Mice

Area of Science:

• Neuroscience
• Otolaryngology
• Gerontology

Background:

• Hearing loss is a known risk factor for age-related cognitive decline.
• The impact of hearing loss on Alzheimer's disease (AD) pathology remains understudied.

Purpose of the Study:

• To investigate the effect of conductive hearing loss (HL) on cognitive function and brain changes in a mouse model of Alzheimer's disease.

Main Methods:

• Utilized the 5xFAD transgenic mouse model for Alzheimer's Disease (AD).
• Induced conductive hearing loss (HL) via chronic tympanic membrane perforation.
• Assessed cognitive function using Y-maze and passive avoidance tests.
• Evaluated brain changes using Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) for glucose metabolism and gray matter concentration.

Main Results:

• Mice with Alzheimer's disease and hearing loss (AD-HL) exhibited exacerbated memory deficits compared to AD mice.
• AD-HL mice showed reduced cerebral glucose metabolism in the frontal association cortex.
• While initial hippocampal and cerebellar glucose metabolism decreased, gray matter differences were not significant at 3 months.
• Significant gray matter reductions were observed in specific brain regions (e.g., cingulate cortex, substantia nigra) in AD-HL mice at 7 months.

Conclusions:

• Conductive hearing loss significantly aggravates memory impairment in the Alzheimer's disease mouse model.
• Hearing loss impacts both cognitive function and brain structure/metabolism in AD.
• Findings suggest a critical link between sensory deficits and neurodegenerative progression in Alzheimer's disease.