Studies the cognitive and neural mechanisms underlying memory, attention, and controlled processing. His research combines computational modeling (using connectionist frameworks), functional neuroimaging (using fMRI and PET methods), and behavioral studies (in normal and clinical populations, and under pharmacological challenge). Ongoing projects include testing model predictions regarding (1) how the prefrontal cortex represents and maintains information in working memory; and (2) how the dopamine neurotransmitter system regulates control over these processes.