ebook_ADHD2019

32 Rohde, Buitelaar, Gerlach & Faraone DMN as controls while changing from a resting state to a task, making them “work with a background noise”. In summary, both structural and functional MRI imaging findings are very variable across studies, suggesting that the neural underpinnings of ADHD are heterogeneous, which is consistent with studies of cognition. Of note, ADHD has also been associated with more global brain changes (i.e., decrease in total brain volume), as well as with localized brain changes in areas outside the frontal-striatal circuits such as the parietal cortices, thalamus, amygdala, and cerebellum, and al- tered activation patterns within other networks such as the default-mode network. NEUROPHYSIOLOGICAL STUDIES. ELECTROENCEPHALOGRAPHY (EEG) AND EVENT-RELATED POTENTIALS (ERP) Neurophysiological studies, EEG and ERP studies report altered electrical brain activity in relation to several cognitive processes as attention, inhibition, and performance monitoring. 101 In the attention domain, selective attention and con- tinuous performance (CPT) tasks indicate issues with orienting to cues and se- lection/resource allocation processes to target stimuli, oddball studies indicated stimulus discrimination and evaluation problems, and distraction tasks indicating attention switching/orienting problems. When considering response inhibition tasks, Stop-signal studies have indicated deficits in response inhibition that were often preceded by differences in earlier attentional components. Similar effects were reported for the Go/Nogo task, with the CPT task indicating issues with res- ponse preparation and response inhibition. The flanker task has indicated con- flict processing and resource allocation issues. Deficient error detection and/or evaluation were identified by attenuated ERN and Pe components in ADHD, with feedback-processing effects also consistently reported. Similarly, atypical patter- ns of socalled resting-state EEG frequency power have been observed, mostly as increased power of low frequency theta activity and/or decreased power of fast beta activit. 102 Excessive theta-beta ratio, however, cannot be considered a reliable diagnostic measure of ADHD, but may be useful as a prognostic measure. 103 Longitudinal work has identified consistent neurophysiological patterns rela- ted to differential outcomes. Children with ADHD persisting into adulthood show increased beta and reduced frontal theta EEG at rest, 104 and ERP markers for reduced cognitive preparation (CNV) and error processing. 105-107 MAGNETOENCEPHALOGRAPHY There are few magnetoencephalography (MEG) studies in ADHD. A study explo- red neural interactions between auditory cortices and the frontal cortices during