Results : In ADHD , deviant prefrontal and cingulate functional activity was associated with increased IA .
Structural alterations were most pronounced in the cingulate cortex .
Subjects with DBDs showed marked cortico‐subcortical dysfunctions .
ADHD and DBDs share similar cortico‐limbic structural and functional alterations .
RI deficits in ADHD highlighted hypoactivity in the dorso/ventro‐lateral PFC , insula , and striatum , while the paralimbic system was primarily dysfunctional in DBDs .
Across disorders , extensively altered cortico‐limbic dysfunctions underlie IA , while RI was mostly associated with aberrant prefrontal activity .
Conclusion : Control network deficits were evidence d across clinical phenotypes in IA and RI .
Dysfunctions at any level within these cortico‐subcortical projections lead to deficient cognitive‐affective control by ascribing emotional salience to otherwise irrelevant stimuli .
HighlightsImpulsive aggression and dysfunctional response inhibition are present in ADHD and DBDs .
Broad fronto‐striatal‐cerebellar dysfunctions have been implicated in ADHD and DBDs .
Prefrontal and cingulate cortical deficits are associated with IA in ADHD.Severe widespread cortico‐subcortical breakdowns are associated with IA in DBDs .
RI deficits have been attributed to hypoactivity in the lateral PFC , insula , and amygdala .
Whether reduced gray matter volumes relate to ADHD and DBDs or if present as an IA epiphenomenon remains debatable .
Background : Although impulsive aggression ( IA ) and dysfunctional response inhibition ( RI ) are hallmarks of attention‐deficit/hyperactivity disorder ( ADHD ) and disrupted behavioral disorders ( DBDs ) , little is known about their shared and distinct deviant neural mechanisms .
Methylphenidate Normalizes Fronto-Striatal Underactivation During Interference Inhibition in Medication-Naïve Boys with Attention-Deficit Hyperactivity Disorder
Youth with attention deficit hyperactivity disorder ( ADHD ) have deficits in interference inhibition , which can be improved with the indirect catecholamine agonist methylpheni date ( MPH ) . Functional magnetic resonance imaging was used to investigate the effects of a single dose of MPH on brain activation during interference inhibition in medication-naïve ADHD boys . Medication-naïve boys with ADHD were scanned twice , in a r and omized , double-blind design , under either a single clinical dose of MPH or placebo , while performing a Simon task that measures interference inhibition and controls for the oddball effect of low-frequency appearance of incongruent trials . Brain activation was compared within patients under either drug condition . To test for potential normalization effects of MPH , brain activation in ADHD patients under either drug condition was compared with that of healthy age-matched comparison boys . During incongruent trials compared with congruent – oddball trials , boys with ADHD under placebo relative to controls showed reduced brain activation in typical areas of interference inhibition , including right inferior prefrontal cortex , left striatum and thalamus , mid-cingulate/supplementary motor area , and left superior temporal lobe . MPH relative to placebo  upregulated brain activation in right inferior prefrontal and premotor cortices . Under the MPH condition , patients relative to controls no longer showed the reduced activation in right inferior prefrontal and striato-thalamic regions . Effect size comparison , furthermore , showed that these normalization effects were significant . MPH significantly normalized the fronto-striatal underfunctioning in ADHD patients relative to controls during interference inhibition , but did not affect medial frontal or temporal dysfunction .  MPH therefore appears to have a region-specific upregulation effect on fronto-striatal activation
Results : In ADHD , deviant prefrontal and cingulate functional activity was associated with increased IA .
Structural alterations were most pronounced in the cingulate cortex .
Subjects with DBDs showed marked cortico‐subcortical dysfunctions .
ADHD and DBDs share similar cortico‐limbic structural and functional alterations .
RI deficits in ADHD highlighted hypoactivity in the dorso/ventro‐lateral PFC , insula , and striatum , while the paralimbic system was primarily dysfunctional in DBDs .
Across disorders , extensively altered cortico‐limbic dysfunctions underlie IA , while RI was mostly associated with aberrant prefrontal activity .
Conclusion : Control network deficits were evidence d across clinical phenotypes in IA and RI .
Dysfunctions at any level within these cortico‐subcortical projections lead to deficient cognitive‐affective control by ascribing emotional salience to otherwise irrelevant stimuli .
HighlightsImpulsive aggression and dysfunctional response inhibition are present in ADHD and DBDs .
Broad fronto‐striatal‐cerebellar dysfunctions have been implicated in ADHD and DBDs .
Prefrontal and cingulate cortical deficits are associated with IA in ADHD.Severe widespread cortico‐subcortical breakdowns are associated with IA in DBDs .
RI deficits have been attributed to hypoactivity in the lateral PFC , insula , and amygdala .
Whether reduced gray matter volumes relate to ADHD and DBDs or if present as an IA epiphenomenon remains debatable .
Background : Although impulsive aggression ( IA ) and dysfunctional response inhibition ( RI ) are hallmarks of attention‐deficit/hyperactivity disorder ( ADHD ) and disrupted behavioral disorders ( DBDs ) , little is known about their shared and distinct deviant neural mechanisms .