The neuropsychiatry of impulsivity.
OBJECTIVE
Impulsive symptoms occur across neuropsychiatric disorders, with important ramifications for everyday functioning and quality of life. This article considers recent developments in the neuropsychological assessment of impulsivity with a focus on the ability to suppress motor responses (response inhibition).


RESULTS
Using objective tests, response inhibition deficits were identified in several neuropsychiatric conditions associated with impulsivity, namely attention deficit hyperactivity disorder, trichotillomania, obsessive-compulsive disorder, and chronic substance abuse. Deficits were also found in unaffected first-degree relatives of attention deficit hyperactivity disorder and obsessive-compulsive disorder patients. Evidence from patients with focal brain lesions and from healthy volunteers using functional MRI and transcranial stimulation implicated the right inferior frontal gyrus in response inhibition. Pharmacological manipulations of the serotonin system had no detectable behavioural effects on response inhibition, whereas manipulations of the noradrenaline system did.


CONCLUSIONS
Neuropsychological assessment shows great promise in the investigation of impulsivity and its brain substrates. These results support a key role for response inhibition, a function linked to the right inferior frontal gyrus, in the manifestation of impulsivity. Measures of response inhibition will contribute to the search for psychiatric endophenotypes, novel treatments, and more optimal diagnostic classification systems for neuropsychiatric disorders.
Chamberlain
Samuel R
SR
aDepartment of Psychiatry, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, UK. src33@cam.ac.uk
Sahakian
Barbara J
BJ
D000203:Activities of Daily Living / Q000523:psychology; D000293:Adolescent; D000328:Adult; D002648:Child; D007174:Disruptive, Impulse Control, and Conduct Disorders / Q000235:genetics / Q000503:physiopathology* / Q000523:psychology; D005625:Frontal Lobe / Q000503:physiopathology*; D006801:Humans; D007266:Inhibition, Psychological; D009483:Neuropsychological Tests; D009638:Norepinephrine / Q000502:physiology; D011788:Quality of Life / Q000523:psychology; D012701:Serotonin / Q000502:physiology
D012701:Serotonin; D009638:Norepinephrine