Impact of contrast sensitivity performance on visually presented neurobehavioral tests in mercury-exposed children

Presentation of neuropsychological tests on a computer screen may involve a visual challenge to the examinee. The possible need for adjustment for vis ual contrast sensitivity on test performance was therefore determined from data on 917 mercury-exposed children who were examined at age 7 years. Cont rast sensitivity was found to be associated with performance on the compute r-assisted Continuous Performance Test. However, it showed similar associat ions with performance on traditional pencil-and-paper tests, especially Ben der Visual Motor Gestalt Test and Wechsler intelligence Scale for Children- Revised (WISC-R) Block Designs. Contrast sensitivity was not associated wit h prenatal mercury exposure, and adjustment for visual function had only a negligible effect on the regression coefficients for mercury as predictor o f neuropsychological deficits. The mercury-associated neurobehavioral defic its are therefore unlikely to be due to mercury-induced visual system dysfu nction causing secondary deficits in cognitive domain testing. Visuospatial processing appears to be a determinant in contrast sensitivity performance , and careful consideration of whether to control for contrast sensitivity in future studies of neurotoxicant effects is therefore recommended. (C) 20 01 Elsevier Science Inc. All rights reserved.