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In four year olds who had been exposed to polychlorinated biphenyls (PCBs) before birth, prenatal exposure was associated with less efficient visual discrimination processing and more errors in short memory scanning. Postnatal exposure was unrelated to cognitive performance. (GLR)

The effect of exposure to neurotoxic substances on cognitive and behavioral development has become an important research focus within developmental psychology in recent years. Research design considerations are critically important in these studies, because random assignment and experimental control of extraneous influences are not possible and effects are often subtle and not seen in every exposed individual. Oversampling from the most highly exposed individuals is usually needed to ensure detection of toxic effects. Valid and reliable assessment must be made of important potential confounders, yet control variables must not be so confounded with exposure as to obscure toxic effects. In the assessment of developmental outcome, apical measures may provide the greatest sensitivity, and narrow-band tests, more information about the specific nature of the impairment. Dose-response analyses can help determine the lowest exposure levels at which deficits are seen ('thresholds').

Four-year-old children exposed prenatally to polychlorinated biphenyls (PCBs), an environmental toxin, were assessed on three tasks - two designed to evaluate cognitive processing efficiency and one to evaluate sustained attention. When compared with standardized IQ tests, these tasks provided greater specificity in identifying cognitive deficits. Adapted for 4-year-old children in the present study, these paradigms demonstrated moderate levels of test-retest reliability. Prenatal exposure to PCBs was associated with less efficient visual discrimination processing and more errors in short-term memory scanning but not with sustained attention. Although much larger quantities of these contaminants are transferred postnatally via breastfeeding than prenatally across the placenta, postnatal exposure was unrelated to cognitive performance. The data link intrauterine PCB exposure to two dimensions of cognitive functioning fundamental to learning.

Tests 242 newborns exposed prenatally to low levels of polychlorinated biphenyls from maternal consumption of contaminated lake fish. The Brazelton Neonate Scale was used to assess behavioral outcomes. Contaminated fish consumption predicted motoric immaturity, poorer labeling of states, a greater amount of startle, and abnormally weak (hypoactive) reflexes. (Author/AS)

Distress in response to brief maternal separations was examined in a sample of 93 predominantly home-reared infants using the Ainsworth strange situation paradigm. At 18 months, the age when separation protests begin to decline, securely attached infants are better able than anxiously attached infants to tolerate maternal separations. (Author/RH)

Examines the psychometric properties of two procedures for reducing data from the Brazelton Neonatal Behavioral Assessment Scale: factor and cluster analysis. The sample consisted of 85 male and 77 female newborns. (RH)