Dynamic topography of visual evoked potential in children: a study of the development of the visual system

To study the development of the visual system, the dynamic topography of the visual evoked potential (VDT) was investigated in 30 normal children aged from two weeks to four years. Twenty-three of the 30 children (77%) showed reliable VDT. The results showed three steps in the development of the visual system in these young children. The first step was seen during the first 4 months after birth, and it was represented by a shortening of duration and an increasing of amplitude in N70 in the occipital region. The second step was seen between 9 months and 2 years of age, and it was represented by a shortening of duration and an increasing of amplitude in P100 and P150 over a widespread area in the occipito-parieto-temporal region. The third step was not clearly seen until 3 years of age, and was represented by the appearance of P200, the so called "vertex potential", around the occipitoparietal region. These three steps in the development of the visual system seemed to be closely related to the time-course of the development in the myelination and maturation of the neuron synapses in the visual pathway and visual cortex. With the aid of VDT, it was possible to clarify that the visual system in children develops step by step from a low level to a high level of the visual function.