Factuality and Mechanisms of Promoting Effect of Hearing Loss on Age-related Cognitive Impairment

Hearing loss (HL) is one of the most common neurological disorders, and produces adverse impacts on human life, not only in the auditory system. It has long been recognized that HL is linked with the development of dementia. Recently, epidemiological evidence suggests a causative role of HL in accelerating the development of dementia. However, the nature of the connection is not really clear due to the fact that many factors are involved in clinical data. The goal of this study is to verify the causative role of HL and to explore the underlying mechanism in a laboratory setting, where confounded factors can be well controlled. Moreover, various studies will be carried out to explore the mechanisms, which cannot be done in human subjects. We have completed several studies to establish a base for the proposed research. We have found a decline of cognitive function in mice after a type of noise induced hearing loss (NIHL) in association with the reduction of new neuron generation in the hippocampus. We have also found functional reorganization in the brain regions that are important for cognitive function using functional magnetic resonance imaging (fMRI). In the proposed study, we will make a comprehensive evaluation of how HL impairs cognitive function in animals. To explore why this is happening, we will measure the HL-induced changes in the generation of new neurons in the hippocampus, which is a critical brain region for learning and memory and the changes of genes that are critical for learning and memory. We will further investigate the changes in the cognitive brain induced by various HLs using fMRI. The research will provide insight on how cognitive brain degenerates in a more general population (people with HL) than that involved in diseases such as Alzheimer's disease, multiple sclerosis etc. The outcome will promote the protection of hearing so to benefit the protection against brain degeneration.