Fractionating impulsivity: neuropsychiatric implications

Although also being a characteristic of normal behaviour, excessive impulsivity is an important symptom of several neuropsychiatric and neurological disorders, including addiction, attention-deficit hyperactivity disorder and Parkinson disease.However, impulsivity may comprise several apparently related forms that depend on distinct neuropsychological processes and neural systems. Of particular importance are interactions between frontostriatal systems and their neurochemical modulation, which are also providing new insights into the functions of these systems in behaviour.The psychological and neural basis of impulsivity can be studied in a mutually profitable way in experimental animals and in humans. Striking parallels can be observed in the underlying neurobehavioural systems, allowing both macro- and micro-definition of functional circuits.The dissection of impulsivity in this Review may represent a way in which complex behaviour relevant to psychiatric disorders can be broken down into its constituent parts, thus allowing for improved genetic understanding and more-precise treatments at the level of symptoms rather than according to categorical diagnoses of mental health disorders.