Sensitivity of Continuous Performance Test (CPT) to Methylmercury Exposure at Age 14 Years

Abstract

ISEE-0186 Background and Objectives: Reaction Time latencies (RT) measured in the Continuous Performance Test (CPT) indicate the speed of information processing. The latencies may be related to different neuropsychological functions depending on the time intervals during the test duration when the responses are assessed: 1-2 minutes with orientation, learning and habituation; the following few minutes with cognitive speed of processing in selective focused attention; and a final period with sustained attention as the dominant demand. Prenatal methylmercury exposure has been associated with increased reaction time latencies at age 7 years in Faroese children. We assessed the association of methylmercury exposure with the average RT in three time intervals at age 14 years. Methods: Exposure levels were determined from mercury concentrations in cord blood, postnatal blood, and hair samples from a Faroese cohort. 878 children completed CPT. RT latencies were recorded during 10 minutes test duration on a task of target stimuli. Regression models were adjusted for confounders. Results: The three sets of CPT-RT outcomes showed different association patterns with methylmercury exposure: the average RT for the first 1-2 minutes was weakly associated with methylmercury (Beta (SE), 2.83 (2.10)); a significant association for the 3-6 minute interval (4.95 (2.23)); and a strongest association for the 7-10 minutes (6.41 (2.45)). This association pattern was unchanged when the scores of Catsys-Reaction Time Test, Finger Tapping Test or CPT-RT (1-2 minutes) were included in the models as confounders to control for simple reaction time and characteristics of learning. No association was found in regard to measures of postnatal exposures. Conclusion: The CPT-RT latencies reflect different functions, as indicated by results separated according to test duration. The findings show that neuropsychological functions related with sustained attention are particularly vulnerable, indicating probable underlying dysfunctions of frontal lobes. This association may be missed, if test results are averaged.