Frequency bands in seeing and remembering: comparing ADHD and typically developing children

This study aimed to examine whether the visual working memory (VWM) phases, encoding and recall, may be impaired in children with Attention Deficit/Hyperactivity Disorder (ADHD). The second aim was to measure electroencephalographic (EEG) correlates of two types of encoding: efficient and inefficient encoding. 23 children with ADHD, age and sex matched with 23 non ADHD subjects, were recruited. With reference to neurophysiological measures, an EEG was recorded before the WMT, during the encoding and finally during the recalling phases of the WMT. With reference to neuropsychological measures, we tested the encoding phase through eye-tracker measures and the recalling phase through the free recall span measure. In comparison to the control subjects, the ADHD group showed lower eye-tracker measurements and free recall span. They also showed lower alpha, beta and theta levels than the control group. Only in the efficient encoding, the control and ADHD groups showed similar beta bands. These results suggest that the ADHD group showed a decrease in the power of nearly all bands.