Executive Function following Developmental Exposure to Polychlorinated Biphenyls (PCBs): What Animal Models Have Told Us

Abstract

Polychlorinated biphenyls (PCBs) were first manufactured in the 1930s for industrial use. While they were eventually banned in the 1970s, their extreme stability allowed them to bioaccumulate over time, such that they remain one of the most prevalent environmental contaminants. A large number of research studies have focused on the neurotoxic properties of PCBs. Interpreting and synthesizing the results of these studies is challenging because special consideration must be given to (a) the class of PCB congeners examined, (b) the age at the time of PCB exposure, and (c) the specific neurological or behavioral function assessed. Nevertheless, animal models of developmental PCB exposure have contributed significantly to our understanding of the specific cognitive domains affected by exposure. In particular, a number of well-controlled experiments using animal models have assessed cognitive function, specifically executive function, following developmental PCB exposure in monkeys and rodents. Generally speaking, executive functions are higher-order cognitive processes involved in the planning, sequencing, and control of goal-directed behaviors. Specifically, these processes include formulating strategies as well as initiating, inhibiting, and shifting responding when necessary.This chapter reviews the experiments examining executive function in animals following PCB exposure. The results of the animal studies are then compared and contrasted with the results of relevant epidemiological studies using cognitive tasks that tap similar functional domains. To provide some background, the different classes of PCB congeners (coplanar vs. ortho-substituted) are reviewed first. A brief summary of the literature on exposure to coplanar PCB congeners in animals during development is included, but coplanar PCBs will not be discussed in detail because they appear to have relatively minor effects on cognitive function. The remainder of the chapter focuses on research examining executive function in animals following exposure to single ortho-substituted PCB congeners as well as PCB mixtures.