| ADHD commonly persists into adulthood and is characterized by deficits in working memory (WM) on neuropsychological testing. We used fMRI to examine the functional neuroanatomy associated with performance of a WM task in ADHD adults and controls. Eight ADHD males (ages 23--30) and 8 demographically-matched healthy males were recruited from a two-decade long, longitudinal study of ADHD. The N-back WM task (1-, 2-, and 3-back) was presented alternately with a control condition (0-back) administered in a block-design format. Whole-brain fMRI was performed on a 1.5T GE scanner. The ADHD group was significantly less accurate than controls on the 1- and 2-back conditions, but not on the 3-back condition. Functional imaging results restricted to the 3-back condition, on which we did not observe group differences in performance, reveal that relative to the controls, the ADHD group exhibited significantly greater activation in the right putamen, right superior parietal lobule (BA 40), right middle frontal gyrus (BA 46), and left thalamus. In contrast, the control group exhibited greater activation in the left lingual gyrus (BA 18), left inferior parietal lobule (BA 7), right precuneus (BA 7), and right middle occipital gyrus (BA 19). These unexpected findings, i.e. ADHD subjects showing overactivity in frontal-striatal and parietal regions, are interpreted in terms of the mediating role of attention in WM processing. In contrast, the relatively greater extrastriate activation in the controls could be related to more efficient perceptual processing during the WM task. |
