FMRI using BOLD technique is an indirect and relative measure of neuronal activity and makes comparison among age groups problematic in light of known age related changes in glucose consumption and resting cerebral blood flow. In this study Arterial Spin Tagging techniques will be used to perform quantitative measures of blood flow changes during fMRI tasks. Children and adults will perform four tasks: primary sensory (photic flash), primary motor (finger tapping), and cognitive (working memory and semantic decision) tasks using parametric block designs, to account for developmental performance, using imaging parameters that allow quantitative measures of cerebral blood flow response as well as BOLD signal. Three age groups will be studied, children 8-10, 14-16, and young adults (21-28). Data will be analyzed using AFNI to identify activated areas. Further analysis will be performed using a region of interest analysis. We will compare quantitative measures at optimal performance levels. The three experimental age groups will be compared for delta rCBF and extent of activated area for each task. The study will determine age dependent changes in blood flow response during cortical activation across ages.