Visual recognition memory deficits in methylmercury-exposed Macaca fascicularis infants.

Infant Macaca fascicularis exposed prenatally to maternal subclinical levels of methylmercury (MeHg) and their nonexposed controls were administered a test of visual recognition memory beginning at 210 days postconception (mean postnatal age = 51.88 days, SD = 5.30). The test consisted of a series of problems in which two identical 35 mm slides of a monkey's face were presented for a study period, followed by a test trial in which the previously exposed stimulus was paired with a novel one, and the looking time to each was recorded. The nonexposed group showed differential visual attention to the novel stimuli, indicating visual recognition abilities. The exposed group's visual attention to the novel stimuli was random. These results, in conjunction with earlier findings, suggest that prenatal MeHg exposure is associated with impaired visual recognition memory performance.