Asymmetrical visual-spatial attentional performance in ADHD: evidence for a right hemispheric deficit

Area of Science:

• Neuroscience
• Developmental Psychology
• Clinical Psychology

Background:

• Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterized by inattention and hyperactivity.
• Visual-spatial attention deficits have been observed in children with ADHD, but the specific hemispheric involvement requires further clarification.

Purpose of the Study:

• To confirm a lateralizing deficit in visual-spatial attention in children with ADHD.
• To characterize the nature of this deficit and identify the likely hemispheric locus of dysfunction.

Main Methods:

• Administered two versions of the covert orienting of attention procedure (evaluating endogenous and exogenous cuing) to 20 unmedicated children with ADHD (aged 9-12) and 20 matched controls.
• Conducted thorough psychiatric assessments and administered the TOVA and Wisconsin Card Sorting Task (WCST).

Main Results:

• Children with ADHD demonstrated an asymmetrical performance deficit.
• This deficit was characterized by a loss of costs in controlled (endogenous) attentional orienting towards invalidly cued left visual field targets.
• The degree of cost asymmetry negatively correlated with WCST performance.

Conclusions:

• Unmedicated children with ADHD exhibit an asymmetrical performance deficit in covert orienting, indicating a disruption of right hemispheric attentional mechanisms.
• This deficit may be associated with reduced right hemispheric frontal-striatal catecholamine activity.