Critical periods of neural development occur during early postnatal life that correspond with increases in synaptic plasticity and the formation of neural circuits needed for learning and memory. This development can be profoundly influenced by experience and negatively affected by environmental toxins. Environmental enrichment and lead exposure inversely affect mediators of synaptic plasticity, which suggests that enrichment may have an attenuating effect on lead induced cognitive deficits. A wealth of evidence has indicated that exposure to excessive amounts of inorganic Pb2+ during early development can produce long lasting cognitive deficits in humans. Evidence also suggests that children raised in an impoverished environment are at a disproportionate risk for developing Pb2+-induced cognitive deficits compared with peers exposed to an enriched environment. The present study evaluated the effects of both developmental Pb2+ exposure and environmental enrichment on visuospatial working and long-term memory in rats. Animals were fed either 1500 ppm Pb2+ acetate-laced rat chow or standard chow and exposed to either an impoverished environment (single housed, bedding only) or an enriched environment (4 rats/cage with toys, enclosures, etc.) for 7 weeks following weaning (PN day 25). Long-term and working memory error rates were assessed during a 17 day radial arm maze (RAM) learning task. Results suggest that the quality of the rearing environment but not Pb2+ exposure had a significant effect on learning performance. These findings suggest that the detrimental effects of Pb2+ exposure on cognitive development may be attenuated by exposure to an enriched environment and that the combination of being reared in an impoverished environment coupled with Pb2+ exposure can significantly impair learning performance later in life.
Tolman, Nicholas, "Combined effects of rearing environment and lead (Pb2+) exposure on visuospatial learning and memory in rats" (2013). Behavioral Neuroscience Honors Papers. 5.
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