This project investigates whether vestibular loss in aging adults predicts hippocampal atrophy. The proposed research will be carried out within the Baltimore Longitudinal Study of Aging (BLSA), a rigorous, comprehensive longitudinal study of >800 individuals age ?60. Specifically, Aim 1 is to determine whether vestibular loss predicts hippocampal atrophy. We hypothesize that vestibular loss predicts subsequent atrophy of the CA1 subfield in the posterior hippocampus where the place cells and head direction cells are predominantly located and most modulated by vestibular input.
Aim 2 is to determine whether vestibular loss predicts atrophy of the major pathways that carry vestibular input to the hippocampus. We hypothesize that vestibular loss predicts atrophy of white matter tracts between the thalamus and hippocampus (e.g. fornix), and between the vestibular cortex and hippocampus (e.g. cingulum). Moreover, our exploratory hypothesis is that vestibular loss predicts atrophy of the main thalamic nuclei that relay vestibular information from the vestibular end-organs and nuclei to the hippocampus (e.g. ventroposterior complex, ventrolateral nucleus, anterior dorsal nucleus). To accomplish these aims, we will use data from the Baltimore Longitudinal Study of Aging (BLSA). BLSA participants undergo vestibular physiologic testing and repeated brain MRI evaluations every 1-2 years. We will evaluate whether changes in vestibular function predict structural hippocampal changes over a 6-year follow-up period (2013-2019) in 80 participants. The BLSA has validated advanced approaches to measure longitudinal changes in gray matter volume and white matter tract integrity. We will also collaborate with colleagues in Computational Anatomy to apply novel methods to measure hippocampal and thalamic shape (i.e. differential atrophy) and sub-field atrophy. These methods can identify the structural basis for neurodegenerative disease with remarkable precision, such as pinpointing the earliest foci of Alzheimer?s disease pathology years before the disease manifests. At the end of this grant, we will gain knowledge about the specific hippocampal sub-fields and potentially the vestibulo-hippocampal circuits that are affected by vestibular loss in aging adults. Future studies will be directed at determining whether hippocampal changes induced by vestibular loss contribute to the onset of Alzheimer?s disease. Because effective vestibular therapies exist, results of these studies will help to determine whether vestibular treatment holds promise for Alzheimer?s disease mitigation.

Public Health Relevance

Vestibular loss is common in older individuals. We observed in prior studies that vestibular loss in aging adults is associated with reduced spatial cognition, which is a commonly-observed feature of dementia and Alzheimer?s disease. In this study, we aim to investigate whether vestibular loss in aging adults predicts hippocampal atrophy, which could be a mechanism by which vestibular loss leads to decline in spatial cognitive function.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Small Research Grants (R03)
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Communication Disorders Review Committee (CDRC)
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King, Kelly Anne
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Johns Hopkins University
Schools of Medicine
United States
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Kamil, Rebecca J; Jacob, Athira; Ratnanather, John Tilak et al. (2018) Vestibular Function and Hippocampal Volume in the Baltimore Longitudinal Study of Aging (BLSA). Otol Neurotol 39:765-771
Adler, Henry J; Anbuhl, Kelsey L; Atcherson, Samuel R et al. (2017) Community network for deaf scientists. Science 356:386-387