This study will look at the impact of dosing as well as ongoing treatment with an investigation medication identified as PF-03654746, on cognitive and physiologic indicators of brain function. Data from this study will assist with the evaluation of the utility of functional magnetic resonance imaging, arterial spin labeling (ASL), and electrophysiologic measures in the detection of early signals of the effectiveness of medications developed to target cognitive impairment in schizophrenia. Safety and tolerability of PF-03654746 in this population will be also be evaluated.