RESUMEN
Performance deficits and diminished brain activity during cognitive control and error processing are frequently reported in attention deficit/hyperactivity disorder (ADHD), indicating a "top-down" deficit in executive attention. So far, these findings are almost exclusively based on the processing of static visual forms, neglecting the importance of visual motion processing in everyday life as well as important attentional and neuroanatomical differences between processing static forms and visual motion. For the current study, we contrasted performance and electrophysiological parameters associated with cognitive control from two Flanker-Tasks using static stimuli and moving random dot patterns. Behavioral data and event-related potentials were recorded from 16 boys with ADHD (combined type) and 26 controls (aged 8-15 years). The ADHD group showed less accuracy especially for moving stimuli, and prolonged response times for both stimulus types. Analyses of electrophysiological parameters of cognitive control revealed trends for diminished N2-enhancements and smaller error-negativities (indicating medium effect sizes), and we detected significantly lower error positivities (large effect sizes) compared to controls, similarly for both static and moving stimuli. Taken together, the study supports evidence that motion processing is not fully developed in childhood and that the cognitive control deficit in ADHD is of higher order and independent of stimulus type.
RESUMEN
Visual motion perception is essential for appropriate behavior in a dynamic visual world. It is influenced by voluntary attention towards or away from moving objects as well as by the capture of automatic attention by salient stimuli. Both kinds of attention play a major role in the Eriksen Flanker Task (EFT),where a central stimulus has to be identified in the presence of flanking distractors. For static visual stimuli incongruent peripheral flankers are known to reduce accuracy rates and prolong reaction times. However,it is not known if a similar flanker effect also affects speeded responses to moving stimuli. We therefore examined whether a flanker effect exists for moving random dot patterns (RDPs) and compared it to the effect elicited by static visual triangles in human subjects. We observed a motion flanker effect,both for response times and accuracy rates. Incongruently moving peripheral flankers caused a slowing of response time and a reduction of accuracy rates compared to congruently moving RDPs. These motion flanker effects were not significantly different from those in the static flanker task. The presence of a motion flanker effect and its similarity to the flanker effect for static stimuli suggests that visual motion engages competitive attention and control mechanisms for perception and decision-making similar to those engaged by non-moving features.
