Implicit time of pattern evoked potentials in infants: an index of maturation of spatial vision.

Pattern reversal visually evoked potentials (VEP) were recorded from preterm infants, term infants, young children and adults. The implicit time of the peak of the first positive wave was measured for different check sizes. The implicit time of the VEP for checks larger than 30′ of arc reaches adult levels by 16–20 weeks of age. The implicit time for checks smaller than 30′ of arc decreases rapidly up to 1 year of age and then slowly until 5–6 years of age suggesting that the plasticity of the human visual system may extend until then. Further, from early infancy to adulthood, patterns comprised of small checks (high spatial frequencies) elicit signals with longer implicit times than stimuli with large checks (low spatial frequencies).