Parallel development of ERP and behavioural measurements of visual segmentation.

Visual segmentation, a process in which elements are integrated into a form and segregated from the background, is known to differ from adults at infancy. The further developmental trajectory of this process, and of the underlying brain mechanisms, during childhood and adolescence is unknown. The aim of the study was to investigate the developmental trajectory of ERP reflections of visual segmentation, and to relate this to behavioural performance. One hundred and eleven typically developing children from 7 to 18 years of age were divided into six age groups. Each child performed two visual tasks. In a texture segmentation task, the difference in event-related potential (ERP) response to homogeneous (no visual segmentation) and checkered stimuli (visual segmentation) was investigated. In addition, behavioural performance on integration of elements into contours was measured. Both behavioural and ERP measurements of visual segmentation differed from adults in 7-12 year-old children. Behaviourally, young children were less able to integrate elements into a contour than older children. In addition, a developmental change was present in the ERP pattern evoked by homogeneous versus checkered stimuli. The largest differences in behaviour and ERPs were found between 7-8- and 9-10-, and between 11-12- and 13-14-year-old children, indicating the strongest development between those age groups. Behavioural as well as ERP measurements at 13-14 years of age showed similar results to those of adults. These results reveal that visual segmentation continues to develop until early puberty. Only by 13-14 years of age, children do integrate and segregate visual information as adults do. These results can be interpreted in terms of functional connectivity within the visual cortex.