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Our ability to understand human cognition will be significantly enhanced if neurotransmitters released during cognitive processing can be detected, mapped and measured in the live human brain.Since neuroimaging techniques have extremely limited ability to detect neurochemical changes, we developed a dynamic molecular imaging technique to detect dopamine released acutely in the live human brain during a task performance.The technique exploits the competition between endogenously released dopamine and its ligand for receptor occupancy.Because of this competition, concentration of a previously administered ligand decreases in the brain areas where dopamine is released during task performance.In this technique values of a number of receptor kinetic parameters are measured before and after task initiation.By comparing these values, dopamine released during task performance is detected, mapped and measured.Using this technique we studied dopamine released inside and outside the striatum during processing of a number of cognitive, emotional and behavioral tasks in healthy volunteers and psychiatric patients.These tasks include conscious and nonconscious memory, emotional processing, executive inhibition and motor planning.We expect that this technique will be used in near future to diagnose psychiatric and neuropsychiatric conditions at an early stage because deficits at this stage are expressed mostly under cognitive or behavioral challenges.More significantly, the technique will allow study of an uninvestigated aspect (neurochemistry) of human cognition and will expand the scope of neuroimaging, cognitive and pharmaceutical research.