REVERSAL-LEARNING TASKS MAY PROVIDE RAPID-DETERMINATION OF COGNITIVE DEFICITS IN LEAD-EXPOSED CHILDREN

An historical cohort study of twins, aged 6 to 15 years, found reduced cognitive performance related to subclinical exposure to lead (Pb) mu ch earlier in life. Pairs of twins discordant for blood Pb (low-Pb twi ns ranged from 30-50 mu g/dl and high-Pb twins ranged from 43-80 mu g/ dl) exhibited reduced learning of a computer-administered visual discr imination and reversal by the twin having the higher exposure. There w as no evidence that sensory or motor impairment contributed to the cog nitive deficit. Performance of a reference group indicated that test's validity for age-related cognitive development and the methods suitab ility for children of varying socio-economic or racial status. Because the reversal learning approach required only one 20-min test session and was powerful enough to document Pb-related deficits in a small sam ple (n = 8), it may indicate a practical method for obtaining early ev idence of environmentally induced developmental delays. An advantage o f the test is that it can be used with both humans and animals. Tests capable of direct comparison of behavioral data from humans and animal s can guide the search for behavioral and biological mechanisms in exp eriments that can be done only with animals. They also can augment the clinical procedures currently used.