RESULTS The fMRI analysis showed that methylpheni date significantly enhanced activation in bilateral inferior frontal cortex (IFC)/insula during inhibition and time discrimination but had no effect on working memory networks .
The meta- analysis , including 14 fMRI data sets and 212 children with ADHD , showed that stimulants most consistently enhanced right IFC/insula activation , which also remained for a subgroup analysis of methylpheni date effects alone .
A more lenient threshold also revealed increased putamen activation .
CONCLUSIONS Psychostimulants most consistently increase right IFC/insula activation , which are key areas of cognitive control and also the most replicated neurocognitive dysfunction in ADHD .
These neurocognitive effects may underlie their positive clinical effects
BACKGROUND Psychostimulant medication , most commonly the catecholamine agonist methylpheni date , is the most effective treatment for attention-deficit/hyperactivity disorder ( ADHD ) .
However , relatively little is known on the mechanisms of action .
Acute effects on brain function can eluci date underlying neurocognitive effects .
We tested methylpheni date effects relative to placebo in functional magnetic resonance imaging ( fMRI ) during three disorder-relevant tasks in medication-naïve ADHD adolescents .
In addition , we conducted a systematic review and meta- analysis of the fMRI findings of acute stimulant effects on ADHD brain function .
Effects of methylphenidate on working memory functioning in children with attention deficit/hyperactivity disorder.
BACKGROUND AND AIMS Children with attention deficit/hyperactivity disorder ( ADHD ) often show deficits in working memory performance .  Methylpheni date ( MPH ) is an effective medication to improve these cognitive difficulties . This study aim ed to clarify which effect MPH induces on the underlying functional networks of working memory . METHODS Fourteen boys diagnosed with ADHD and 12 healthy controls were investigated using functional magnetic resonance imaging ( fMRI ) . Each patient was tested twice , once with medication and once without . The fMRI experiments consisted of three verbal N-back tasks with increasing difficulty . Functional images were acquired on a 3 Tesla head scanner . RESULTS On the behavioral level , medicated patients performed similar to healthy controls and significantly better than without medication . On the functional level , patients showed the expected frontal and parietal activations , which were more pronounced in the 2- and 3-back tasks . Healthy controls showed significantly more activation in these regions and additional activation in the cerebellum . Interestingly , patients showed an additional effect of laterality . Left-sided frontal and parietal activation in patients was significantly less pronounced than in controls . CONCLUSION Functional data indicate different activation patterns in verbal working memory tasks between healthy controls and patients with ADHD irrespective of medication condition . Intake of MPH led to a clear improvement on a behavioral level . However , this effect was not reflected by changes in functional brain organization . MPH-induced changes leading to better performance in verbal working memory tasks might be very subtle and therefore not detectable by fMRI
RESULTS The fMRI analysis showed that methylpheni date significantly enhanced activation in bilateral inferior frontal cortex (IFC)/insula during inhibition and time discrimination but had no effect on working memory networks .
The meta- analysis , including 14 fMRI data sets and 212 children with ADHD , showed that stimulants most consistently enhanced right IFC/insula activation , which also remained for a subgroup analysis of methylpheni date effects alone .
A more lenient threshold also revealed increased putamen activation .
CONCLUSIONS Psychostimulants most consistently increase right IFC/insula activation , which are key areas of cognitive control and also the most replicated neurocognitive dysfunction in ADHD .
These neurocognitive effects may underlie their positive clinical effects
BACKGROUND Psychostimulant medication , most commonly the catecholamine agonist methylpheni date , is the most effective treatment for attention-deficit/hyperactivity disorder ( ADHD ) .
However , relatively little is known on the mechanisms of action .
Acute effects on brain function can eluci date underlying neurocognitive effects .
We tested methylpheni date effects relative to placebo in functional magnetic resonance imaging ( fMRI ) during three disorder-relevant tasks in medication-naïve ADHD adolescents .
In addition , we conducted a systematic review and meta- analysis of the fMRI findings of acute stimulant effects on ADHD brain function .