Assessment of visual capacity in full-term neonates as a function of behavioural state was investigated with the luminance flash visual evoked potential (VEP). Infant state (quiet sleep, active sleep, quiet wakefulness, active wakefulness) was determined by behavioural observation and polygraphic recording of EEG, eye movements, electrocardiogram, electromyogram and respiration. VEPs were recorded across the sleep/waking cycle only under carefully defined state conditions. The results indicate that state dramatically effects the amplitude, latency and waveform of the transient luminance flash VEP with the most significant differences between sleep and wakefulness. The results further suggest that controlled state recording reduces intra and intersubject VEP variability.

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