Executive dysfunction in attention-deficit/hyperactivity disorder: cognitive and neuroimaging findings

Attention-deficit/hyperactivity disorder has been associated with a prominent disturbance of executive functions. There is no pathognomic neuropsychological profile for the disorder, however. Nonetheless, results of neuropsychological testing, in concert with other clinical information,provide a more comprehensive and detailed picture of the individual patient's cognitive and emotional strengths and weaknesses than a psychiatric diagnostic interview alone. This approach to the evaluation of ADHD therefore can provide a strong objective basis from which to make patient-specific recommendations for compensatory strategies and treatment. It should be noted, however, that although executive dysfunction in the form of impaired response inhibition remains the most prominent cognitive theory of ADHD, other theories have been put forth that also deserve further investigation. These include a disturbance in delay aversion (referring to intolerance for waiting) and impaired temporal processing, among others [79]. The neural substrates of executive dysfunction in ADHD have begun to be revealed by a growing body of structural and functional neuroimaging research. Although still in its infancy, neuroimaging of ADHD is pointing toward disruption of FSTC circuitry and the cerebellum as being central to the cognitive and motor abnormalities seen in the disorder. Further research using cognitive tasks assessing executive functions in combination with functional imaging techniques will provide further insight into the etiology of the disorder. It is expected that advances in structural and functional neuroimaging will yield valuable information that will facilitate the differential diagnosis of ADHD. Evidence cited suggests that psychostimulant medication can improve executive functions and their underlying FSTC circuitry. Furthermore, a recent study of adults with ADHD found significant improvements in organization skills and other symptoms of ADHD following cognitive remediation targeting several executive and emotional aspects of the disorder [80]. Additional studies investigating the effects of treatment on executive dysfunction and brain integrity in ADHD will be necessary to determine the degree to which the structural and functional brain abnormalities observed are mutable. Finally, because the myriad cognitive, behavioral and emotional symptoms in ADHD likely reflect the interplay of multiple cognitive and psychosocial factors, development of treatments for ADHD likely will require a multi-modal approach.