ERPs in Controls and ADHD Patients During Dual N-Back Task

Abstract

Attention Deficit/Hyperactivity Disorder (ADHD) is a behavioral disorder of childhood and adolescence characterized by symptoms that include impulsiveness, inattention, hyperactivity, impaired decision making, and primary deficits of executive functions. In a vast proportion of the diagnosed adolescents, the clinical symptoms may persist into adulthood and ADHD patients are characterized by Working Memory (WM) impairment. In the present study, we analyze brain dynamics by EEG recordings during the dual n-back task in a population of young adults with ADHD and healthy controls. The WM capacity and attention span are tested by n-back task, and divided attention is tested by running the task in the visual and auditory modalities concurrently. We analyzed the event-related potentials (ERPs) triggered by the onset of the audio-visual stimuli. In ADHD the amplitude of N200 wave component was only slightly reduced and the peak latency was unaffected. The amplitude of P300 peak was reduced in ADHD with respect to controls at all sites along the midline. The latency of P300 peak in ADHD was reduced at Fz and Cz. In particular, at Fz the latency of ADHD was reduced after a response that required matching the visual cue 1 or 2 trials back in time. These results support the hypothesis that the P300 component, associated with a cognitive workload, peaked earlier in the ADHD than in controls and it may be used to follow the outcome of cognitive training.