Measuring infant memory: Utility of the visual paired-comparison test paradigm for studies in developmental neurotoxicology.

The assessment of brain function and behavior in young infants is central to understanding the effects of chemical exposure on central nervous system development. One approach to infant cognitive assessment, based on the direct observation of infant eye movements, is known as the Visual Paired-Comparison task. The Visual Paired-Comparison test methodology uses selective visual attention as a vehicle to study emerging recognition memory skills. The utility of this procedure to study visual recognition memory has been well established in both human and nonhuman primate infants. The primary outcome measure produced by this assessment technique is known as the Novelty Preference Score, reflecting the amount of time the infant spends actively looking at novel rather than familiar test stimuli. Visual recognition memory testing has demonstrated a strong sensitivity to conditions that may place infants at risk for poor developmental outcome (e.g. preterm birth, Down syndrome) and in humans; performance is significantly related to later measures of I.Q. and language competency. This assessment methodology has been successfully applied to the study of neurobehavioral effects after fetal neurotoxicant exposure. Field and laboratory studies have used tests of visual recognition memory to better understand the effects of compounds such as lead, methylmercury and polychlorinated biphenyls on emergent cognitive processing. The Visual Paired-Comparison paradigm and its capacity to measure recognition memory in preverbal infants provides a valid and theoretically meaningful approach to neurobehavioral assessment for studies in developmental toxicology and teratology.