Academic journal article Environmental Health Perspectives

Response Inhibition and Error Monitoring during a Visual Go/no-Go Task in Inuit Children Exposed to Lead, Polychlorinated Biphenyls, and Methylmercury

Academic journal article Environmental Health Perspectives

Response Inhibition and Error Monitoring during a Visual Go/no-Go Task in Inuit Children Exposed to Lead, Polychlorinated Biphenyls, and Methylmercury

Article excerpt

BACKGROUND: Lead (Pb) and polychlorinated biphenyls (PCBs) are neurotoxic contaminants that have been related to impairment in response inhibition.

OBJECTIVES: In this study we examined the neurophysiological correlates of the response inhibition deficits associated with these exposures, using event-related potentials (ERPs) in a sample of schoo-lage Inuit children from Arctic Quebec exposed through their traditional diet.

METHODS: In a prospective longitudinal study, we assessed 196 children (mean age, 11.3 years) on a visual go/no-go response inhibition paradigm. Pb, PCB, and mercury (Hg) concentrations were analyzed in cord and current blood samples. Hierarchical multiple regression analyses were conducted to examine the associations of contaminant levels to go/no-go performance (mean reaction time, percent correct go, percent correct no-go) and five ERPs [N2, P3, error-related negativity, error positivity (Pe), and correct response positivity (Pc)] after control for confounding variables.

RESULTS: Current blood Pb concentrations were associated with higher rates of false alarms and with decreased P3 amplitudes to go and no-go trials. Current plasma PCB-153 concentrations were associated with slower reaction times and with reduced amplitudes of the Pe and Pc response-related potentials. Hg concentrations were not related to any outcome on this task but showed significant interactions with other contaminants on certain outcomes.

CONCLUSIONS: These results suggest that Pb exposure during childhood impairs the child's ability to allocate the cognitive resources needed to correctly inhibit a prepotent response, resulting in increased impulsivity. By contrast, postnatal PCB exposure appears to affect processes associated with error monitoring, an aspect of behavioral regulation required to adequately adapt to the changing demands of the environment, which results in reduced task efficiency.

KEY WORDS: event-related potentials, error monitoring, executive function, lead, methylmercury, neurotoxicity, polychlorinated biphenyls, response inhibition. Environ Health Perspect 120:608-615 (2012). http://dx.dolorg/10.1289/ehp.1103828 [Online 5 December 2011]

Lead (Pb) and polychlorinated biphenyls (PCBs) are widespread environmental contaminants known for their developmental neurotoxicity. Despite differences in their chemical structures and properties, early exposure to these pollutants appears to produce similar effects on neurobehavior, including impulsivity, hyperactivity, and impairment in executive function (Boucher et al. 2009a; Brothel and Cory-Slechta 1998; Nicolescu et al. 2010; Rice 1999). These effects have been hypothesized to reflect dysfunction of the prefrontal cortex (Levin et al. 1992; Meng et al. 2005) and alterations in dopamine function (Seegal et al. 1997; White et al. 2007).

The term "executive fUnction" refers to a set of cognitive processes involved in goal-directed behaviors, which are often elicited in new and/or complex situations (Norman and Shallice 1986). One key component of executive function is the ability ro inhibit dominant or prepotent responses when necessary (Miyake et al. 2000), and impairment in this ability can result in impulsivity. Studies investigating the relation of Pb and PCB exposure to impulsivity and executive function have relied exclusively on neuro-psychological and observational assessments. Because of their high temporal resolution, event-related potentials (ERPs) make it possible to evaluate children's performance in specific response components arrayed across time. ERPs recorded during a task requiring response inhibition could help in understanding the neurobehavioral effects associated with Pb and PCB exposures in children.

The Inuit from Nunavik (Arctic Quebec, Canada) are among the most heavily exposed populations on earth to PCBs and methyl-mercury (MeHg) because of the long-range transport of these chemicals via atmospheric and ocean currents and their bioaccumulation in fish and sea mammals that are staples of the traditional Inuit diet (Muckle a al. …

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