Invited Symposium: What Can Genetic Models Tell Us About Attention-Deficit Hyperactivity Disorder (ADHD)?
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Performance data
Stop task
No differences were observed between adults and adolescents in mean reaction time or probability of inhibition. The hyperactive group showed a trend to be faster than healthy adolescents on the go-trials (t-test, p < .06) and to inhibit less often on the inhibition trials (t-test, p = .10).Delay task
Adults showed a more accurate time estimation than adolescents; their mean synchronization time calculated as absolute mean deviation time from stimulus onset was smaller (t-test, p = .02). However, no differences were observed in the variability of the time estimations. No group differences were observed between healthy and psychiatric adolescents in the mean synchronization time nor its variability. There was no significant correlation between any of these measures of delay and stop task performance during scanning and non-verbal IQ.Imaging data
There were no significant differences between groups in any mode of stimulus correlated motion estimated during performance of either stop or delay tasks.Stop task
Generic activation in adults was observed in predominantly right inferior frontal lobe (approximate Brodmann area (BA) 45), right anterior (BA 32) and posterior cingulate (BA 31), bilateral premotor cortex (BA 6) and Supplementary Motor Area (SMA). Generic activation in adolescents was in right mesial frontal cortex (BA 8/32), right medio-inferior prefrontal lobe (BA 9/45), right SMA (BA 6) and right and left caudate nuclei. Adolescents with ADHD activated right pre- and postcentral gyrus (BA 4/3/2/1), right inferior parietal lobe (BA 40), and right caudate nucleus.
Figure 1
Figure 1 shows generic brain activation in the three groups. Distance from the AC/PC line is indicated in mm.
ANOVA analysis shows that adults compared to adolescents show increased power of response in bilateral premotor cortex (BA 6), while adolescents show increased response in right caudate and left insula. Healthy adolescents compared to psychiatric adolescents showed significantly g reater power of functional response in right mesial frontal cortex (BA 8/32), in right inferior frontal lobe (BA 45/9) and in predominantly left caudate nucleus.
Delay task
Group activation in adults was in mesial frontal cortex (BA 32), bilateral inferior frontal lobe and insula (BA 47), in right rostro-dorsolateral prefrontal, right putamen, posterior cingulate and extrastriate cortex (BA 31/19). Healthy adolescents activated right anterior and posterior cingulate (BA 32/31), right SMA and bilateral extrastriate cortex (BA 19).Adolescents with ADHD activated left and right putamen, right SMA (BA 6) and right extrastriate cortex (BA 18).Figure2
Figure 2
ANOVA shows that adults compared to adolescents show increased response in anterior (BA 32) and posterior cingulate (BA 23), in right inferior frontal lobe (BA 45), in right putamen, and in left parietal lobe (BA 40). Healthy adolescents compared to the psychiatric group showed increased power of response in anterior (BA 32) and in posterior cingulate (BA 31) and left parietal lobe (BA 40). A focus of increased power of response in the hyperactive group was observed in right SMA (BA 6).
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