Development of visual function: a neurophysiological point of view

Recent findings on the development of visual function in children are summarized. First, visual evoked potentials (VEPs) in normal school children, following two types of visual stimuli (pattern reversal and light emitting diode stimulation) by transient and steady-state stimulation, are presented. Reproducible VEPs with the 4 stimulation conditions can be obtained. Transient and steady-state methods provide complementary results. Second, mechanisms for photosensitive epilepsy (PSE) are discussed. We recorded flicker VEPs to different color combinations and quantified the effects of changes in color and luminance combinations. Two amplitude peaks (9 and 18 Hz) were observed for all kinds of isoluminant color combination stimuli against temporal frequency. In addition, this characteristic was modulated by luminance. Normal children showed much higher sensitivity to contrast changes and color combination compared with normal young adults, which may be responsible for PSE in childhood. Third, cognitive function for facial expression of normal children and adults is mentioned. For Chernoff's faces showing anger and sadness produced by computer, children showed higher scores compared with adults, suggesting higher sensitivity for facial expression. Knowledge of developmental changes in children allows us to understand the maturational and degenerative changes of the central nervous system.