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 .
A right hemispheric frontocerebellar network for time discrimination of several hundreds of milliseconds
Debate still surrounds the nature of the role of the dorsolateral prefrontal gyrus ( DLPFC ) in time perception . This region is frequently associated with working memory and is thus implicated as a so-called " accumulator " within a hypothesized internal clock model . However , we hypothesized that this region may have a more primary role in time perception . To test this hypothesis we used functional magnetic resonance imaging ( fMRI ) to examine the neural correlates of relatively pure time perception with a temporal discrimination task where intervals of 1 s had to be discriminated from those of 1.3 , 1.4 , and 1.5 s. Time perception in this particular time domain within the " perceived present " has not previously been investigated using fMRI . By using relatively short time periods to be discriminated and also contrasting activation with an order judgment task , we aim ed to minimize the confounding aspects of sustained attention and working memory . In a group of 20 healthy right-h and ed adult males , neural activation associated with time discrimination was found in a predominantly right hemispheric network of right dorsolateral and inferior prefrontal cortices , right supplementary motor area , and left cerebellum . We conclude that right DLPFC , rather than having a purely working memory function , might be more central ly involved in time perception than previously thought
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 .