Event-related slow-wave activity in two subtypes of attention-deficit/hyperactivity disorder

Objective: Previous time–frequency studies have indicated that event-related low-frequency activity has important effects on component topography and developmental effects in auditory event-related potentials (ERPs) of children and adolescents. This study investigated the influence of event-related slow-wave (SW) (0.01–2 Hz) activity in the group differences seen between children with and without attention-deficit/hyperactivity disorder (AD/HD) of different subtypes. Methods: Time–frequency analysis techniques were applied to auditory ERP data derived from children with AD/HD predominantly inattentive type (n=30), AD/HD combined type (n=30) and age-matched control subjects (n=30). Results: Event-related early frontal negative and late posterior positive SW components were reduced in the AD/HD combined type group, but not AD/HD inattentive type group, relative to controls. The RESIDUAL ERPs, which represented event-related 2–12 Hz activity, showed clinical vs. control group differences in components that were similar in both AD/HD subtype groups. Conclusions: The time–frequency results showed that event-related SW (0.1–2 Hz) activity contributes importantly to group differences between AD/HD and control children, and the pattern of group differences from controls for each of the AD/HD subtype groups, which are evident in raw ERPs. These results emphasise both the clinical and developmental importance of this form of analysis. Significance: This novel approach revealed additional specific information about stimulus processing and regional inhibition/activation in two AD/HD subtypes, relative to control subjects.