RESULTS In ADHD patients the middle and inferior frontal gyri , basal ganglia , and cerebellum were most often affected by MPH .
The middle and inferior frontal gyri were frequently affected by MPH during inhibitory control tasks .
Throughout nine task-based fMRI studies investigating MPH 's effect on the brains of pediatric patients with ADHD , MPH result ed in increased activation within frontal lobes , basal ganglia , and cerebellum .
In most cases , this increase " normalized " activation of at least some brain areas to that seen in typically developing children
OBJECTIVE Attention-deficit/hyperactivity disorder ( ADHD ) is a psychiatric disorder affecting 5 % of children .
Methylpheni date ( MPH ) is a common medication for ADHD .
Studies examining MPH 's effect on pediatric ADHD patients ' brain function using functional magnetic resonance imaging ( fMRI ) have not been compiled .
The goals of this systematic review were to determine ( 1 ) which areas of the brain in pediatric ADHD patients are modulated by a single dose of MPH , ( 2 ) whether areas modulated by MPH differ by task type performed during fMRI data acquisition , and ( 3 ) whether changes in brain activation due to MPH relate to clinical improvements in ADHD-related symptoms .
Therapeutic Doses of Oral Methylphenidate Significantly Increase Extracellular Dopamine in the Human Brain
Methylpheni date ( Ritalin ) is the most commonly prescribed psychoactive drug in children for the treatment of attention deficit hyperactivity disorder ( ADHD ) , yet the mechanisms responsible for its therapeutic effects are poorly understood . Whereas methylpheni date blocks the dopamine transporter ( main mechanism for removal of extracellular dopamine ) , it is unclear whether at doses used therapeutically it significantly changes extracellular dopamine ( DA ) concentration . Here we used positron emission tomography and [(11)C]raclopride ( D2 receptor radiolig and that competes with endogenous DA for binding to the receptor ) to evaluate whether oral methylpheni date changes extracellular DA in the human brain in 11 healthy controls . We showed that oral methylpheni date ( average dose 0.8 + /- 0.11 mg/kg ) significantly increased extracellular DA in brain , as evidence d by a significant reduction in B(max)/K(d ) ( measure of D2 receptor availability ) in striatum ( 20 + /- 12 % ; p < 0.0005 ) . These results provide direct evidence that oral methylpheni date at doses within the therapeutic range significantly increases extracellular DA in human brain . This result coupled with recent findings of increased dopamine transporters in ADHD patients ( which is expected to result in reductions in extracellular DA ) provides a mechanistic framework for the therapeutic efficacy of methylpheni date . The increase in DA caused by the blockade of dopamine transporters by methylpheni date predominantly reflects an amplification of spontaneously released DA , which in turn is responsive to environmental stimulation . Because DA decreases background firing rates and increases signal-to-noise in target neurons , we postulate that the amplification of weak DA signals in subjects with ADHD by methylpheni date would enhance task-specific signaling , improving attention and decreasing distractibility . Alternatively methylpheni date -induced increases in DA , a neurotransmitter involved with motivation and reward , could enhance the salience of the task facilitating the " interest that it elicits " and thus improving performance
RESULTS In ADHD patients the middle and inferior frontal gyri , basal ganglia , and cerebellum were most often affected by MPH .
The middle and inferior frontal gyri were frequently affected by MPH during inhibitory control tasks .
Throughout nine task-based fMRI studies investigating MPH 's effect on the brains of pediatric patients with ADHD , MPH result ed in increased activation within frontal lobes , basal ganglia , and cerebellum .
In most cases , this increase " normalized " activation of at least some brain areas to that seen in typically developing children
OBJECTIVE Attention-deficit/hyperactivity disorder ( ADHD ) is a psychiatric disorder affecting 5 % of children .
Methylpheni date ( MPH ) is a common medication for ADHD .
Studies examining MPH 's effect on pediatric ADHD patients ' brain function using functional magnetic resonance imaging ( fMRI ) have not been compiled .
The goals of this systematic review were to determine ( 1 ) which areas of the brain in pediatric ADHD patients are modulated by a single dose of MPH , ( 2 ) whether areas modulated by MPH differ by task type performed during fMRI data acquisition , and ( 3 ) whether changes in brain activation due to MPH relate to clinical improvements in ADHD-related symptoms .