Neurophysiological Basis for Functional Connectivity Changes in Early Alzheimer’s Disease

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Abstract Early diagnosis and treatment of Alzheimer’s disease (AD) are critical for delaying the onset of clinical symptoms, such as cognitive impairments and memory deficits. Early in AD, cognitively normal individuals who are positive for amyloid-β, a predictive biomarker of AD, exhibit a transient increase in brain connectivity prior to a decline in brain connectivity and cognition. This hyper-connectivity phase of AD suggests a prodromal pathology that may be exploited as an early biomarker prior to the onset of clinical symptoms. Though these changes in brain network connectivity have been well documented, little is known about the underlying neuropathology. I seek to test whether localized increases in excitatory neuronal activity caused by amyloid-β drive the brain-wide hyper- connectivity observed in early AD. I will use a multimodal imaging approach to determine the impact of amyloid- β on neuronal and glutamate activity on the scale of the neuron (microscopic), regional neuronal circuit (mesoscopic), and inter-regional network connectivity (macroscopic) in mouse models of AD. My proposal comprises the following three aims: Aim 1: Determine the impact of acute exposure of amyloid-β on neuronal, glutamate, and network activity in the normal cortex, Aim 2: Determine the impact of chronic, progressive amyloid-β accumulation on neuronal, glutamate, and network activity in a young mouse model of AD, and Aim 3: Determine how total glutamate concentration changes, measured by translational magnetic resonance spectroscopy, relate to synaptic glutamate activity changes with disease progression. Together, these experiments could determine the neurophysiological underpinnings of the connectivity changes observed in early AD. Data from this study could introduce novel treatment strategies for patients at risk of developing AD. Furthermore, this work closely integrates my clinical interest in neuroimaging and neurology. In addition to rigorous mentored research training, this proposal includes clinical experience and professional development that will facilitate my growth into an independent physician-scientist.