Structural and functional imaging approaches in attention deficit/hyperactivity disorder : does the temporal lobe play a key role?

Attention deficit/hyperactivity disorder (ADHD) is characterized by widespread structural and functional abnormalities in the brain. We applied different structural imaging techniques such as voxel-based morphometry (VBM), diffusion tensor imaging (DTI), and magnetization transfer imaging (MTI) to study anatomical differences between boys with ADHD and healthy controls, as well as functional magnetic resonance imaging (fMRI) together with independent component analysis (ICA) to detect functional alterations. 14 boys with ADHD and 12 controls were included in our study. Results of DTI showed the expected differences in frontal and cerebellar white matter. VBM and MTI indicated group differences in the temporal lobe. Applying ICA to fMRI data, we extracted four components; two positively correlated to our working memory paradigm and two negatively correlated. Positive components included activation in frontal and parietal regions. Negative components showed activation in anterior and posterior cingulate cortex/precuneus and temporal regions, and were interpreted as forming part of the default mode network. Group differences in the inferior temporal lobe were detected. Applying different techniques, we found differences between boys with ADHD and controls mainly located in the temporal lobe. Therefore, we postulate that research on ADHD should broaden its scope by including the temporal lobe as a potentially important locus of abnormalities in ADHD.