Associations between developmental exposure to environmental contaminants and spatial navigation in late adolescence.

Inuit communities in Northern Quebec (Canada) are exposed to environmental contaminants, particularly to mercury, lead and polychlorinated biphenyls (PCBs). Previous studies reported adverse associations between these neurotoxicants and memory performance. Here we aimed to determine the associations of pre- and postnatal exposures to mercury, lead and PCB-153 on spatial navigation memory in 212 Inuit adolescents (mean age = 18.5 years) using a computer task which requires learning the location of a hidden platform based on allocentric spatial representation. Contaminant concentrations were measured in cord blood at birth and blood samples at 11 years of age and at time of testing. Multivariate regression models showed that adolescent mercury and prenatal PCB-153 exposures were associated with poorer spatial learning, whereas current exposure to PCB-153 was associated with altered spatial memory retrieval at the probe test trial. These findings suggest that contaminants might be linked to different aspects of spatial navigation processing at different stages.

Characterizing the Effects of Enchroma Glasses on Color Discrimination.

SIGNIFICANCE: Enchroma glasses were designed to improve color vision among color-blind individuals. The putative aid of such optic filters in alleviating color blindness remains to be demonstrated. Our study shows that the beneficial impacts on color discrimination are quite small in comparison to the undesirable effects. PURPOSE: Congenital color blindness is a common genetic anomaly, and there is still no effective aid for affected people. Enchroma glasses are selective filters designed to enhance color discrimination among red-green color-blind individuals. However, there is a lack of data supporting their efficiency. The present study aimed to characterize the effect of Enchroma filters on color discrimination. METHODS: Colorimetric coordinates of figures from a pseudoisochromatic (American Optical Hardy-Rand-Rittler [AO H-R-R]) test were measured. Nine color-blind and five control adult participants performed the AO H-R-R test and a color-naming task using monochromatic stimuli. All data were collected with and without Enchroma filters. RESULTS: Colorimetric coordinates of AO H-R-R figures were shifted out of their respective pseudoisochromatic line. The AO H-R-R error scores of participants with color blindness were not clearly improved by the filters except for the protanopic subgroup. However, the filters promoted a change in the classification of the defect, specifically by increasing protan errors in deutan participants. In the color-naming task, Enchroma filters impaired perception in all participants, specifically for cyan stimuli. CONCLUSIONS: Enchroma filters may affect the nature of a color vision deficiency without necessarily alleviating its severity. Although the performance of protan participants increased in the pseudoisochromatic task with Enchroma filters, this was the only improvement observed across tasks and subgroups. In summary, this study does not support the efficacy of Enchroma filters in correcting color discrimination in color-blind individuals.

Environmental toxic agents: The impact of heavy metals and organochlorides on brain development.

Exposure to environmental toxicants can have deleterious effects on the development of physical, cognitive, and mental health. Extensive laboratory and clinical studies have demonstrated how the developing brain is uniquely sensitive to toxic agents. This chapter focuses on the main neurologic impairments linked to prenatal and postnatal exposure to lead, methylmercury, and polychlorinated biphenyls, three legacy environmental contaminants whose neurotoxic effects have been extensively studied with respect to cognitive and behavioral development. The main cognitive, emotion regulation, sensory, and motor impairments in association with these contaminants are briefly reviewed, including the underlying neural mechanisms such as neuropathologic damages, brain neurotransmission, and endocrine system alterations. The use of neuroimaging as a novel tool to better understand how the brain is affected by exposure to environmental contaminants is also discussed.