Visual evoked potentials(VEPs) are the cerebral electrical activities recorded from the occipital scalp following a flash or pattern stimulation and can detect the lesions of sensory visual pathways. Although the VEPs change with the maturation of CNS in children, a few studies have documented the maturational changes in premature infants. Using the light- emitting diode goggles, VEPs were studied in 131 neurologically intact infants of 28∼41 weeks gestational age or 34∼59 weeks postmenstrual age.

The VEPs were analysed by three waveforms; normal, abnormal, and flat, and four patterns; N₃₀₀, P₂₀₀-N₃₀₀, P₁₀₀-N₁₅₅-P₂₀₀-N₃₀₀, and P₁₀₀ pattern. Normal waveforms were 63 of 131 VEPs(48.1%). Of the normal waveforms, N₃₀₀ patterns were 38.1%, P₂₀₀-N₃₀₀ 36.5%, P₁₀₀-N₁₅₅-P₂₀₀-N₃₀₀ 19.0%, and P₁₀₀ 6.4%. Each pattern correlated with the postmenstrual age. These findings support the hypothesis of VEP pattern changes according to the maturation of the visual system with age.

Many factors have been identified which to affect the rate of propagation of impulses along motor fibers. These include temperature changes around the nerve, diameter of the axon, degree of myelinization, age of infants, and local environment of the nerve. Motor nerve conduction velocity and Hoffman's reflex latency have been used to assess the degree of myelination and maturation of the nervous system. The conduction velocities in infants of a short gestational age are significantly lower than those of the fullterm infants. The extrauterine myelination and maturation might increase nerve conduction velocity. We measure the median motor nerve conduction velocity, compound muscle action potentials amplitude and H-reflex latency of premature infants to determine the neurological maturation after birth. The premature infants with gestational age above 37 weeks have a significantly higher conduction velocity and a shorter H-reflex latency than those of gestational age below 37 weeks. The premature infants with weight over 2.5 kg have a significantly higher conduction velocity, larger compound muscle action potentials amplitude and a shorter H-reflex latency than those of weight below 2.5 kg. And there is a statistically significant negative correlation of the H-reflex latency with the postmenstrual age. The determination of motor nerve conduction velocities and H-reflex latencies seem to be an additional method in assessing the degree of maturity in infants after birth.