Some rats in the experiment were raised on a diet that was rich in fish oil, specifically an omega-3 fatty acid known as DHA (docosahexaenoic acid). Some people suggest DHA might ease the neurotoxic effects of methylmercury, but DHA did not ameliorate the effects of methylmercury in this study at all. When rats on this diet were tested at middle age (about 15-18 months), they committed a substantial number of errors. (Intensive behavior therapy during the experiment mitigated these effects, and even the most seriously affected rats did well after this intervention.)

Paletz says the findings suggest that methylmercury produces behavioral rigidity in rats and that fish oil does not mitigate these effects. He says the findings have potential implications for human health: the children of women who were exposed to methylmercury during their pregnancies might have impairments that affect them later in life whenever "the rules change" in learning situations.

Paletz conducted this research for his Ph.D. dissertation at Auburn University.

CONTACT: Elliott Paletz, (608) 262-4780, paletz@wisc.edu

Methylmercury in groundwater in a Lake Superior watershed:
Wednesday, Aug. 9, 2006, 10 a.m., Hall of Ideas: Mercury contaminates watersheds around Lake Superior, and naturally-occurring bacteria convert this mercury into its most toxic form - methylmercury. Scientists have known for many years that these toxic transformations occur in wetlands and lake sediments: studies in Michigan's Upper Peninsula documented similar transformations in groundwater. Researchers from UW-Madison worked on
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Contact: Kathleen Schmitt
media@mercury2006.org
608-262-6393
University of Wisconsin-Madison
3-Aug-2006