Attention-deficit hyperactivity disorder (ADHD) in adults is understudied, especially regarding neural mechanisms such as oscillatory control of attention sampling. We report an EEG study of such cortical oscillations, in ADHD-diagnosed adults taking a continuous performance test that measures the ability to sustain attention and inhibit impulsivity for a prolonged period of time.We recorded 53 adults (28f, 25m, aged 18-60), and 18 matched healthy controls, using 128-channel EEG. We analysed features with established links to neural correlates of attention: event-related (de)synchronisation (ERS/D), alpha and theta frequency band activation, phase-locking value (PLV), and timing-sensitivity indices; in frontal and parietal scalp regions.Test performance distinguished healthy controls from ADHD adults. The ADHD group manifested significantly less parietal pre-stimulus 8Hz theta ERS during correct inhibition trials, less frontal & parietal post-stimulus 4Hz theta ERS during inhibition & response trials, and increased frontal & parietal pre-stimulus alpha ERS during inhibition & response. They showed significantly reduced fronto-parietal connectivity that lagged across trials and was strongly lateralised. In addition, they had reduced sensitivity to targets in stimulus-locking measures.Building on the hypothesis of parietal attention sampling, our results suggest that ADHD adults have impaired attention sampling in relational categorisation tasks.
Reduced power in fronto-parietal theta EEG linked to impaired attention-sampling in adult ADHD
