Development of Shape Processing within the Dorsal and Ventral Pathways: A Near Infra-Red Spectroscopy (NIRS) Study
Over the past 30 years researchers have expanded their understanding of object processing in infancy. In contrast, little is understood about the neural mechanisms that underlie this capacity, in large part because few techniques are available to measure brain functioning in infants. Recently, developmental scientists have explored near-infrared spectroscopy (NIRS), an optical imaging technique that uses changes in blood volume as an index of neural activation, as a method to assess the relation between brain and cognitive development.
Chronic, low dose prenatal exposure to methylmercury (MeHg) impairs mnemonic function in adult C57/B6 mice
Methylmercury (MeHg) exposure is associated with a variety of cytotoxic effects including damage to the central nervous system (CNS). It is well known that the developing CNS is extremely vulnerable to MeHg-induced deficits in comparison to the mature brain. However, phenotypic outcomes that occur in adult offspring exposed developmentally to the neurotoxic effects of chronic, low dose MeHg are not well-characterized. The objective of this study was to determine the effects of chronic, low dose, prenatal MeHg exposure on mnemonic function in adult male and female mice. Developing mouse fetuses were exposed in utero during gestational days 8-18 by giving pregnant C57Bl/6J female mice food containing MeHg at a daily dose of 0.01 mg/kg body weight. Prenatally exposed, adult mice (5 to 8 months) were then trained on both hidden (spatial) and visible (cued) versions of the Morris water maze. Mice prenatally exposed to MeHg were spatially impaired, demonstrating significantly longer swim paths to the hidden platform than saline-exposed controls. Importantly, sensorimotor and/or motivational deficits were not responsible for these spatial deficits as both groups performed comparably on the cued (visible platform) version of the maze. No main effects of Sex were observed in any of the analyses. These results indicate that prenatal exposure to even low dosages of MeHg can have long-lasting cognitive consequences in adulthood and that medial temporal lobe structures (e.g., hippocampus) are putative targets for the deleterious effects of this environmental toxin.
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