Early Biomarkers of Alzheimer's Disease: Using Speech Markers to Detect Mild Cognitive Impairment

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PROJECT SUMMARY Detecting early signs of Alzheimer’s disease (AD) and mild cognitive impairment (MCI) during the prodromal stage of AD is becoming increasingly important for cost-effective clinical trials, developing targeted intervention strategies, and gaining maximum benefit from currently available treatment plans. However, because of substantial differences in the manifestation of cognitive impairment, preclinical cognitive changes are not discernible from age-related cognitive decline. Although a combined approach of using neuropsychological, fluid, and imaging biomarkers has relatively improved the timely diagnosis of AD, measurement of these biomarkers is expensive and highly technology- dependent, making these techniques impractical for use in many older adults across different settings. In addition, assessment of cognitive functions through the use of neuropsychological batteries remains the gold-standard in clinical trials and evaluation of intervention efficacy. Thus, it is critical to identify early detectors that are 1) sensitive to pathologies of AD, 2) strongly predictive of future change in cognition, and 3) accessible and feasible across diverse settings. Based on our recent findings, which have identified measures of speech motor control as a powerful aid in indexing early stages of neurodegenerative diseases such as amyotrophic lateral sclerosis and primary progressive aphasia, we propose assessment of speech markers as an alternative or complementary and ecologically valid strategy for identifying adults at risk of developing cognitive impairment due to AD. Speech production is one of humans’ most complex motor behaviors, as it relies on tight integration of cognition, sensory, and motor processes which are all subject to change with advancing age. We hypothesize that the rate of age-related changes in speech motor control of adults can be influenced by genetic susceptibility to develop AD. In addition, we hypothesize that measures of speech elicited during cognitively-demanding speech tasks can differentiate carriers of APOE ε4 (i.e., the major gene known to increase AD risk) from noncarriers and that baseline speech acoustic and kinematic measures can predict later cognitive decline. The proposed research will innovatively use acoustics and articulatory kinematics in combination with neuroimaging to pursue three Aims. In Aim 1, we will determine the effect of aging on speech motor control of adults with APOE ε4 positive (ε4+) and APOE ε4 negative (ε4-) genotypes matched in sex and education. In Aim 2, we will identify the brain structural and resting-state functional bases for age-related changes in speech measures of adults with ε4+ and ε4- genotypes. Finally, in Aim 3, we will determine 1) whether baseline speech acoustic/ kinematic measures predict cognitive change over two years, as quantified by Hopkins Learning Test- Revised (HVLT-R) and Trail Making Test (TMT) scores in ε4+ and ε4- groups and 2) if speech and cognitive changes are mediated through alterations in brain structure and function. The findings of this study will provide critical information about measures of speech motor control that can be efficiently incorporated into neuropsychological testing to optimize the clinical assessment of AD.