Neural dysfunction in ADHD with Reading Disability during a word rhyming Continuous Performance Task.

BACKGROUND

Attention-Deficit/Hyperactivity Disorder (ADHD) is a heterogeneous, neurodevelopmental disorder which co-occurs often with Reading Disability (RD). ADHD with and without RD consistently have higher inattentive ratings compared with typically developing controls, with co-occurring ADHD and RD also demonstrating impaired phonological processing. Accordingly, inattention has been associated with greater phonological impairment, though the neural correlates of the association are poorly understood from a functional neuroimaging perspective. It was postulated that only the co-occurring subgroup would demonstrate hypoactivation of posterior, left hemispheric, reading-related areas and, to a lesser extent, alterations in right hemispheric, attention areas compared with controls.

METHODS

A novel word rhyming Continuous Performance Task assesses functional activation differences in phonology- and attention-related areas between three groups: ten boys with ADHD and RD, fourteen boys with ADHD without RD, and fourteen typically developing controls. Subjects respond to words that rhyme with a target word as mono- and disyllabic, English words are visually presented over 90s blocks.

RESULTS

Behavioral performance was not different between groups. Some hypoactivation of left hemispheric, reading-related areas was apparent in ADHD and RD, but not ADHD without RD, compared with controls. Right hemispheric, attention areas showed alterations in both ADHD subgroups relative to controls; however, the differences for each subgroup were dissimilar.

CONCLUSIONS

The dorsal decoding subnetwork may not be grossly compromised in ADHD with Reading Disability. The role of cognitive impairments, including the level of inattention, on phonology requires clarification from a neuroimaging perspective.