Developmental changes in the human visual system as reflected by the latency of the pattern reversal VEP

Abstract

Pattern reversal visually evoked potentials (VEPs) were recorded from 439 infants and young children ranging in age from 1 month to 5 years in response to large and small checks. Qualitative analysis of the VEP wave form showed that the first major positive component, P 1, is consistently present at all ages, while the frequency of occurrence of later positive components is more variable. The proportion of infants showing late positive components increases with age; by 1 year, the frequency of occurrence of late components for large checks is more adult-like than for small checks. The latency of P 1 was analyzed quantitatively. Results showed that P 1 latency decreases rapidly during the first year of life for both large and small checks and that the time course of the latency change differs as a function of check size. VEPs to large checks attain adult-like P 1 latency values by about 1 year of age, while the P 1 latency of VEPs to small checks has still not reached adult levels by 5 years of age. Data from 12 infants tested longitudinally between 1 and 7 months of age using both checkerboards and square wave gratings show no difference in P 1 latency between checkerboards and gratings comprised of large (30–240 min) pattern elements, but for patterns with small (7.5 and 15 min) elements, P 1 latency to checks is significantly longer than P 1 latency to stripes. These results are explained on the basis of the difference in the fundamental spatial frequency between checks and stripes.