CHAPMAN LAB (formerly Johnson)
Specific Research Projects
Hippocampal neurovascular function in health and disease
We are focused on understanding neurovascular mechanisms by which cognitive decline occurs in healthy aging that is accelerated during chronic hypertension and cerebrovascular disease. Specifically, we investigate the novel role of the small arterioles perfusing the ischemic-prone hippocampus in healthy cognitive aging and vascular cognitive impairment and dementia using rodent models. We determine hemodynamic and cognitive consequences of age- and hypertension-induced hippocampal vascular dysfunction, including changes in basal blood flow, neurovascular coupling, neuroplasticity, learning and memory. We are interested in understanding sex differences in hippocampal vascular dysfunction, particularly in the post-menopausal state that may increase the susceptibility of the hippocampus and its vasculature to damage and promote vascular dementia. Combined in vivo and ex vivo methodologies include: studying the function of isolated and pressurized hippocampal arterioles via pressure myography, measuring absolute hippocampal perfusion using hydrogen clearance, assessing neurovascular coupling by measuring simultaneous changes in hippocampal blood flow during a spatial navigation task, determining neuroplasticity using hippocampal slice electrophysiology, and investigating the trajectory of cognitive decline using behavioral tests of learning and memory. The overall goal is to understand the function of hippocampal arterioles and hippocampal hemodynamics in order to develop strategies to protect the hippocampus from hypoxic/ischemic injury during aging and disease states associated with vascular dementia to slow cognitive decline and maintain neurocognitive health.
The role of the hippocampal vasculature in post-stroke dementia during chronic hypertension
We are interested in understanding how transient focal cerebral ischemic stroke affects the hippocampus to promote post-stroke memory impairment and dementia, despite the hippocampus being outside of the ischemic brain region. Using an established rat model of chronic hypertension and intravascular filament model of ischemic stroke (transient middle cerebral artery occlusion, tMCAO), we investigate how tMCAO affects the hippocampal vasculature. Several aspects of vascular function are of interest, including the function of isolated and pressurized hippocampal arterioles studied in vitro, basal and activity-dependent changes in hippocampal blood flow (i.e. neurovascular coupling) determined in vivo, and the integrity of the hippocampal blood-brain barrier as measured using in vivo and in vitro methodology. The overall goal is to understand vascular mechanisms of post-stroke memory impairment in the hopes to develop therapeutic strategies that improve cognitive function of stroke survivors.