Disorder-specific dysfunctions in patients with attention-deficit/hyperactivity disorder compared to patients with obsessive-compulsive disorder during interference inhibition and attention allocation

Abstract

Background: Abnormalities in inhibitory control and underlying fronto-striatal networks is common to both attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive-disorder (OCD). The aim of this study was to investigate disorder-specific abnormalities in neural networks mediating interference inhibition and selective attention.

Method: Event-related functional magnetic resonance imaging (fMRI) was used to compare brain activation of boys with ADHD (18), with OCD (10), and healthy boys during (20) during a Simon task that measures interference inhibition and controls for and therefore comeasures attention allocation.

Results: During interference inhibition, both patient groups shared mesial frontal dysfunction compared to controls. Disorder-specific dysfunctions were observed in OCD patients in dorsolateral prefrontal cortex during the oddball condition and in ADHD patients in inferior parietal lobe during interference inhibition and in caudate and posterior cingulate during the simpler oddball condition. The decreased activation in caudate and cingulate in ADHD was furthermore negatively correlated with ADHD symptoms and positively with OCD behavioral traits.

Conclusions: The study shows that ADHD and OCD patients have shared but also disorder-specific brain dysfunctions during interference inhibition and attention allocation. Both disorders shared dysfunction in mesial frontal cortex. Disorder-specific dysfunctions, however, were observed in dorsolateral prefrontal cortex in OCD patients and in caudate, cingulate, and parietal brain regions in ADHD patients. The disorder-specific dissociation of striato-cingulate activation that was increased in OCD compared to ADHD patients, was furthermore inversely related to the symptomatology of the two disorders, and may potentially reflect differential dopamine modulation of striatal brain regions.

Figure 1

Schematic representation of the fMRI Simon task. Subjects respond to the iconic information (direction of arrow) and have to inhibit the predominant tendency to respond to the spatial information in incongruent trials (side of arrow appearance). In oddball trials the stimulus is congruent but slightly slanted.

Figure 2

Axial slices for the group activation maps for the three groups at P < 0.05 for voxel and P < 0.01 for cluster levels for the (a) Oddball condition (oddball—congruent trials) (b) Simon condition (incongruent—oddball trials). Red = Controls; Green = ADHD; Blue = CD. Overlapping brain regions: Yellow: overlap between ADHD and Controls; Magenta: overlap between CD and Controls. Cyan: overlap between ADHD and CD. White: overlap between all groups. Talairach z‐coordinates are indicated for slice distance (in mm) from the inter‐commissural line. The right side of the picture corresponds to the right side of the brain. For the ADHD group in the oddball‐congruent contrast a cluster p value of P < 0.025 is shown as they showed no activation at P < 0.01.

Figure 3

Axial sections showing the ANCOVA results for the between‐group differences in brain activation at P < 0.05 for voxel and P < 0.01 for cluster levels for the contrast of (a) Oddball condition (Oddball—congruent trials). The activation cluster in right dorsolateral prefrontal cortex was disorder‐specifically reduced in patients with OCD when compared to healthy controls and ADHD patients, while the activation cluster in posterior cingulate and caudate was disorder‐specifically reduced in ADHD compared to both OCD and controls. (b) Simon condition (Incongruent ‐ oddball trials). The cluster in SMA/anterior cingulate was reduced in both patient groups compared to healthy controls. The right inferior parietal activation, however, was specifically reduced in ADHD patients compared to both healthy controls and OCD patients. Talairach z‐coordinates are indicated for slice distance (in mm) from the inter‐commissural line. The right side of the picture corresponds to the right side of the brain.