The project described in this application aims to position arterial spin labeling (ASL) perfusion measurement as a significant, practical tool for the study of brain function. We propose to develop an arterial spin labeling system by combining the use of a separate labeling coil for continuous labeling with a Turbo-ASL scheme and fast, reverse spiral acquisition of the images, for added optional BOLD sensitivity. With this infrastructure in place, the main thrust of this project will be to develop the experimental design and analysis protocol to carry out event-related functional MRI experiments based on cerebral perfusion measurements. This will require the development of a new mathematical model for quantification of perfusion from ASL signal. The project will also involve characterization of the perfusion response to single events, as observed by ASL, as well as a comprehensive study of the statistical properties of the temporal and spatial noise in ASL time series data. Our team of investigators has extensive experience in ASL and BOLD imaging, image acquisition, and the statistical processing of functional images, and is therefore well suited to be successful on the proposed project. In the long term, we hope to go beyond the scope of this proposal and develop the methodology to make quantitative time series measurements of perfusion and use the knowledge gained about the perfusion impulse response function to better understand the BOLD response from a quantitative physiological point of view. These developments will be quite instrumental to the use of ASL perfusion imaging as a powerful tool for the study of brain function.