Preventing age-related cognitive decline: The role of speech processing deficits in dementia

Responsible: Dr. Nathalie Giroud
Duration of the project: August 1st 2019 – December 31st 2020

The Alzheimer’s dementia (AD) prevalence is expected to double in the next 20 years leading to immense personal, social, and health care costs. After 20 years of unsuccessfully trying to find a cure, an alternative way to approach this problem is to identify modifiable risk factors which may delay the onset of AD for individuals at risk. Hearing loss (HL) has been estimated to be the modifiable risk factor with the highest potential impact on risk reduction, if treated properly. However, current approaches to assess and treat HL mainly target peripheral HL (pHL), an age-related decline of the inner ear functions, while next to nothing is known about how to assess, characterize, and treat central HL (cHL), an age-related decline of auditory circuits of the brain leading to speech perception deficits. Yet, speech perception deficits have been shown to lead to communication problems, social isolation, and higher rates of depressive symptoms, which are all strong risk factors for AD and strongly tied to cognitive decline in aging.

This project will develop novel neuroimaging protocols based on the powerful approach of concurrent hierarchical tracking (CHT) disentangling neural responses evoked specifically by distinct acoustic/linguistic processing levels along the auditory and language pathways in the brain. In a large sample of older individuals (65-80 years) with varying degree of pHL who are affected by AD as well as healthy controls, electroencephalography (EEG) and auditory brainstem responses (ABR) will be recorded while participants are presented with (un)predictable, (un)chopped, foreign, and proper continuous speech allowing to systematically characterize the interplay between pHL, cHL, cognitive decline, and bottom-up and top-down driven speech perception mechanisms at different hierarchical neural stages. All participants will undergo comprehensive demographic, neuropsychological, and audiological screening as well as cognitive and speech perception testing.

In sum, this research will be the first to comprehensively describe the neural link between speech perception deficits and cognitive decline in older adults by applying novel neuroimaging techniques. The results of this research will provide the basis to outline new ways for improved, early, and efficient AD-risk screening and consequently delay the onset or progression of the disease by avoiding increasing risks.

1. Giroud, N.*, Keller, M.*, & Meyer, M. (in preparation). Neuroanatomical characteristics of speech in noise perception in older adults with mild presbycusis. *shared first authorship.
2. Jagoda, L., Wehrli, J., Kurthen, I., Neuschwander, P., Meyer, M., & Giroud, N., (in preparation). Neural entrainment is impaired in older adults with hearing loss. An EEG-based audiovisual speech study.

Keywords: speech perception, Alzheimer’s disease, neuroimaging, age-related hearing loss

Funding source(s): Postdoc Forschungskredit of the University of Zurich, Nr. FK-19-072

Partners: Prof. Dr. Volker Dellwo. Dr. Sandra Schwab, Dr. Elisa Pellegrino