Transient flash VEPs allow objective assessment of visual function and are easily recorded in young infants. However, due
to their high variability, they are an insensitive surrogate marker of visual development. The aim of our study was to investigate
the early maturation of temporal characteristics of steady-state flicker VEPs. Data from 53 VEP sessions were analyzed in
term-born infants between birth and 20 months of age. The stimulus was a square-wave modulated luminance flicker with 80%
modulation depth at temporal frequencies of 4.7, 7.5, 12.5, and 19 Hz. A total of 18 healthy adults aged between 21 and 54 years
served as controls. Contingent on the stimulus frequency, we found pronounced changes of the flicker VEP with age. Regression
lines fit to the first harmonic VEP magnitude as a function of age between 3 and 88 weeks of age indicated increases at 7.5
(
P = 0.004), 12.5 (
P < 0.001), and 19 Hz (
P = 0.07) and a non-significant decrease at 4.7 Hz (
P = 0.3). The magnitude of the second harmonic increased for all frequencies (4.7 (
P = 0.05), 7.5 (
P = 0.01), 12.5 (
P = 0.13), and 19 Hz (
P = 0.18)). Over the whole infant age range, the flicker VEP was dominated by the first harmonic, in contrast to adults, where
the response was typically shifted to a higher harmonic at low stimulus frequencies. The optimal stimulus frequency, defined
as the frequency eliciting the highest magnitude for F1, shifted to higher rates with age. Due to the difference from adult
responses, further developmental changes of the temporal properties must be assumed to occur after the age of 20 months. Changes
in temporal characteristics of the flicker VEP with age may be useful as an indicator of visual system maturation and a useful
tool to detect visual delay.
Keywords Flicker VEP - Infant - Maturation - Temporal frequency