Task-specific hypoactivation in prefrontal and temporoparietal brain regions during motor inhibition and task switching in medication-naive children and adolescents with attention deficit hyperactivity disorder.
OBJECTIVE
A relatively small number of functional imaging studies of attention deficit hyperactivity disorder (ADHD) have shown abnormal prefrontal and striatal brain activation during tasks of motor response inhibition. However, the potential confound of previous medication exposure has not yet been addressed, and no functional imaging study exists to date on medication-naive children and adolescents with ADHD. The aim of this study was to investigate the neural substrates of a range of motor and cognitive inhibitory functions in a relatively large group of children and adolescents with ADHD who had never previously been exposed to medication.


METHODS
Nineteen boys with ADHD and 27 healthy age- and IQ-matched boys underwent functional MRI to compare brain activation during performance of tasks that assessed motor response inhibition (go/no go task), cognitive interference inhibition (motor Stroop task), and cognitive flexibility (switch task).


RESULTS
Boys with ADHD showed decreased activation in the left rostral mesial frontal cortex during the go/no go task and decreased activation in the bilateral prefrontal and temporal lobes and right parietal lobe during the switch task. No significant group differences were observed during motor Stroop task performance.


CONCLUSIONS
Abnormal brain activation was observed in medication-naive children and adolescents with ADHD during tasks involving motor inhibition and task switching, suggesting that hypoactivation in this patient group is unrelated to long-term stimulant exposure. Furthermore, functional abnormalities are task-specific and extend from frontostriatal to parietal and temporal cortices.
Smith
Anna B
AB
Department of Child Psychiatry, Institute of Psychiatry, King's College, London, SE5 8AF, UK.
Taylor
Eric
E
Brammer
Mick
M
Toone
Brian
B
Rubia
Katya
K
D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis* / Q000503:physiopathology; D001931:Brain Mapping; D000697:Central Nervous System Stimulants / Q000009:adverse effects / Q000627:therapeutic use; D002540:Cerebral Cortex / Q000503:physiopathology*; D002648:Child; D003072:Cognition Disorders / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D007266:Inhibition, Psychological; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008297:Male; D009048:Motor Skills / Q000502:physiology; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D010296:Parietal Lobe / Q000503:physiopathology; D017397:Prefrontal Cortex / Q000503:physiopathology; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013647:Task Performance and Analysis; D013702:Temporal Lobe / Q000503:physiopathology
D000697:Central Nervous System Stimulants