Perceiving and estimating the passage of time is a fundamental cognitive process, which sub serves many other higher-order cognitive functions, including memory and motor planning? Most theories of timing incorporate the same basic elements: a timekeeper, a temporal template stored in working memory (WM), and a comparator that matches this template to the current stimulus. Attention interacts with these sub-components to influence our overall perception of time. For example, attention directed towards or away from temporal task demands prolongs or shortens the perceived duration. Also, attention itself is distributed across time. For example, directing attention to specific moments in time speeds responding to expected stimuli. I propose to use functional magnetic resonance imaging (fMRI) to compare the neuroanatomical bases of these two distinct aspects of temporal attention. Furthermore, event-related fMRI will be used to dissociate regions linked to attentional aspects of timing from those linked to other components, such as timekeeping or WM. Finally, task-specific changes in brain activity during the presence or absence of neuromodulatory drugs (specifically dopaminergic and cholinergic antagonists) will define the anatomical substrates of the neurochemical modulation of time estimation. Identifying the functional, anatomical and neurochemical mechanisms of temporal attention will not only provide a greater theoretical understanding of timing, but may pave the way for clinical research into the link between cognitive and motor timing dysfunction in Parkinson's disease.