Measurement of right frontal lobe functioning and attention-deficit/hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is one of the most frequently diagnosed behavior problems among children referred for assessment and treatment. In recent years, neuropsychologists have considered ADHD as involving impaired executive functions (i.e., frontal lobe deficits) that may contribute to the central inattention and hyperactive-impulsive symptoms. Further, neurophysiological and neuroimaging findings have supported the involvement of prefrontal circuits in ADHD, particularly in the right hemisphere. Integration of the theoretical and neurophysiological literature on ADHD led to the current investigation of the disorder with measures purportedly sensitive to right frontal functioning. The present study investigated whether measurement of one area of executive dysfunction that has been theoretically linked in part to right frontal functioning would be of greater utility in identifying ADHD than previous, less specific cognitive measures.

The participants included 40 boys aged 8-11 years of age who fulfilled current diagnostic criteria for ADHD. Forty sex-matched controls were also recruited. Each participant was individually assessed via a neuropsychological screening battery, which included intellectual functioning, achievement screening, bilateral and left frontal tests, sustained attention test, and tests specific to right frontal functions. It was found via a multivariate analysis of covariance that the combined measures (associated with bilateral frontal functioning and a measure of sustained attention) significantly differed between those with ADHD and without the disorder. Follow-up analyses revealed that, in particular, three components of the neuropsychological screening battery. Star Cancellation's missed stars, the Design Fluency Test's (DFT) complexity ratio, and the Wisconsin Card Sorting Test's (WCST) preservative responses aided in the discrimination of ADHD boys versus similarly aged controls. Further, it was found that when controlling for the effects of sustained attention, the multivariate effect of the measures in differentiating the groups' performances was no longer present. Exploratory analyses in regard to ADHD comorbid groups were also made. Limitations to the assessment of ADHD, particularly in regard to comorbidity, are also discussed. Overall, it appears that some frontal lobe- based measures, i.e., tests that are less structured, may be of clinical use in discriminating ADHD. Nevertheless, continued research in the area is needed.