Researchers at the University of Montreal, Canada, studied spectral analysis of non-REM sleep (stages 2, 3 and 4) and REM sleep EEG in 6 boys (age 10.3 +/- 1.2) with ADHD compared to 6 healthy controls. None had comorbidities, and none had received methylphenidate for at least 48 hours. Compared to controls, ADHD boys had less slowwave activity (SWA;0.75-2.25 Hz) in frontal and parietal regions. The findings point to an impairment of the thalamo-frontocortical loop in ADHD. 
COMMENT. Previous studies of the waking EEG in ADHD children by the above authors had found abnormalities in frontal, temporal, parietal and occipital regions. Researchers from the Universities of Wollongong and Sydney, Australia, report that increased delta and theta in frontal regions in unmedicated girls with ADHD was normalized by treatment with methylphenidate. Stimulant medication in ADHD girls may improve processing deficits rather than increasing arousal levels. 
Epileptiform activity in the EEG is reported with varying frequency from 7% to 30% of children with ADHD [3, 4]. Methylphenidate treatment of ADHD complicated by centrotemporal rolandic spikes in the EEG has a risk of precipitating seizures in 16.7% compared to only 0.6% in patients with normal EEGs. [5, 6]. For a comprehenive review of ADHD and epilepsy comorbidity, see Schubert R 2005, in .