Response Inhibition in ADHD as revealed by event-related potentials (ERP's)

Here I post some interesting findings on behavioral inhibition in attention deficit hyperactivity disorder as revealed by event-related potentials (ERP's). ERPs are measured on the scalp while the participant is performing a task. Repeated presentation of stimuli results in a brainwave component that is associated with the particular task. In patients with ADHD, respons inhibition is one of the most impaired in its cognition (Liotti, Pliszka, Perez, Luus, Glahn, and Semrud-Clikeman, 2007). The core symptoms of ADHD are attentional impairments, hyperactivity, impulsivity as well as problems in the inhibition of responses (American Psychiatric Association, 1994). The neural generators of response inhibition can be investigated with a high amount of temporal resulation by recording ERP's from the subject's scalp. In the experiment of Liotti et al. (2007) children with ADHD performed on the Stop Signal Task (SST). Briefly, the participants had to make a discrimination among the letters 'A' and 'B', Which were the 'go' stimuli In which they had to respond either with their left or right index finger. Go stimuli were presented with different delays in time Which were equally possible. When an 'S' appeared on screen, this was the stop signal and occured in twenty-five percent of the cases. When subjects saw an 'S' they had to inhibit their response. Electrophysiologically, several brain wave were found to be abnormal in children with ADHD Compared to the healthy children control group. The Stop Signal N200 wave was found to be largly reduced in ADHD children. The source of this ERP component was to be found reduced in right inferior frontal parts of the brain (Liotti et al., 2007). The NoGo (Stop) attenuation is suggested be due to early inhibitory impairments in ADHD. In addition to a reduced N200 ERP component, also the Stop Signal NoGo P3 was found to be reduced.