The enzyme COMT metabolises catecholamines and catecholestrogens,and is particularly important for the metabolism of dopamine in the cerebral cortex. Its activity is strongly influenced by polymorphisms in the COMT gene (notably Val158Met), which in turn correlate with behavioral and neural measures during performance of cognitive tasks, with developmental IQ trajectories, and with risk for several psychiatric phenotypes. COMT is also a therapeutic target, with COMT inhibitors being used in Parkinson’s disease, and in schizophrenia, and with preclinical and clinical evidence that COMT inhibition can improve aspects of cognition. MEG is being used to to identify whether and how the Val158Met polymorphism in COMT influences neural activity associated with cognitive, motivational, and emotional processing and also to characterise whether and how pharmacological inhibition of COMT influences the same functions,either as a main effect or as an interaction with genotype.