Electrophysiological Evidences of Inhibition Deficit in Attention-Deficit/Hyperactivity Disorder During the Attentional Blink

Previous studies on the distribution of attentional resources during time have yielded a differential performance in patients with Attention-Deficit/Hyperactivity Disorder (ADHD), in relation to healthy controls. The Attentional Blink (AB) experimental paradigm probes the ability to discriminate visual stimuli in close temporal proximity. The electro- physiological mechanisms underlying the AB have been intensively studied in healthy individuals, and seems to be very appropriate to evaluate the temporal distribution of attentional resources in ADHD. We recorded Event-Related Potentials (ERPs) to stimuli arranged in a rapid serial visual presentation task. Fourteen male children (age: 11.6±2.1) who met DSM-IV criteria for ADHD of the combined subtype participated in the study, along with fourteen age and sex-matched healthy controls (11.2±2.3). They were all screened to discard comorbidites. Behavioral responses showed an increased number of commission and omission errors in the ADHD group. Nonetheless, both groups exhibited a significant AB for probes presented in close temporal proximity to targets. ERP waveforms in ADHD showed a P300 component of reduced amplitude, elicited both by detected and undetected probes. However, in the control group the P300 was only elicited by detected probes and its amplitude was larger. As the P3 component is considered to reflect context updating in working memory, its elicitation by missed probes during the attentional blink suggests a failure of an inhibitory selection mecha- nism in ADHD.