Quantifying vascular influences on neurovascular coupling with fMRI. (360G-Wellcome-090199_Z_09_Z)

The fMRI BOLD signal is not a direct measure of neuronal activity. When comparing groups, the implicit assumption that neurovascular coupling properties are equivalent is made. Any alterations in cerebrovascular dynamics lead to BOLD differences that are unrelated to neuronal activity. Using an elderly group as a model for altered coupling, this proposal will investigate such BOLD differences, thus developing suitable correction strategies. The project has three main objectives that are inco rporated into an fMRI-cerebrovascular modelling framework: 1) Quantify the influence of dynamic cerebral autoregulation on the BOLD signal to account for blood pressure-related perfusion fluctuations; 2) Account for vascular reactivity-related changes in BOLD signals, thus providing a novel marker of cerebrovascular health; 3) Translate these cerebrovascular models into young/elderly group comparisons by testing their ability to characterise group differences that are present in MEG-derived neur onal activity measures. Since normal ageing and many clinical conditions are accompanied by alterations in microvasculature, fMRI will be unreliable unless appropriate corrections for neurovascular coupling differences are made. Modelling strategies that address these concerns not only increase the robustness of normal ageing fMRI studies but translate to many clinical conditions that are more frequent in the ageing population such as hypertension, dementia and diabetes.