Executive functions in patients with ADHD: An EEG-examination

Introduction: Patients with impulse control deficits often show cognitive abnormalities. Underlying neurophysiological mechanisms can be assessed by means of evoked potentials. In the present study an adapted auditory go/nogo-paradigm was used to investigate electrophysiological correlates in patients with ADHD. Methods: 31 patients with ADHD and 31 healthy subjects were investigated. All participants were free of psychotropic drugs. During the go condition subjects were instructed to immediately press a button in response to the stimuli; during the nogo condition the response was to be inhibited. In the voluntary selection task participants were allowed to freely decide whether to press the button or not. Evoked potentials were recorded by a 32-channel EEG system. Results/Discussion: Reaction times were slower in the voluntary selection condition compared to the go task in either group. Response inhibition and voluntary selection processes were related to a fronto-central negativity after 200 ms (N2) and positivity after 300 ms (P3) in healthy subjects. In the patients P3 was reduced during nogo and voluntary selection conditions. In wavelet analyses patients showed less delta- and theta-activity compared to healthy subjects. The results indicate fronto-central dysfunctions in patients with ADHD in comparison to healthy controls especially in inhibitory processes.