By observing that older male nonhuman primates' spatial memory, which is responsible for recording environmental and spatial-orientation information, declines at a greater rate than that of females, researchers led by Agnès Lacreuse, PhD, assistant research professor, and James Herndon, PhD, associate research professor, both in Yerkes' Division of Neuroscience, concluded a species' sex may influence age-related cognitive decline.
"Given that spatial memory is sensitive to sex differences in humans and in nonhuman primates, we decided to focus our study on determining how cognitive aging differs between the sexes," said Lacreuse. According to Lacreuse, such sex differences have not been studied frequently in humans, and when they have, the data has been inconsistent.
In the study, the researchers observed a large group of young and elderly nonhuman primates performing tasks that measured spatial memory. The researchers presented each animal with an increasing number of identical disks for which the animals had to identify the disk appearing in a new location.
"We saw young adult male nonhuman primates outperform females, a finding consistent with human data that shows men have a higher capacity than women for maintaining or updating spatial information. What's particularly interesting, however, was the finding among older adult nonhuman primates. While we observed cognitive decline in both sexes, the sex difference no longer existed among aged male and female nonhuman primates. This finding suggested the males' spatial abilities declined at a greater rate as they got older than did the females."
The researchers' next steps are to determine what factors may contribute to the differential cognitive decline between males and females. An example is testosterone, which is known to decline in older men and also to affect spatial memory in male humans and rodents. The researchers also hope to conduct imaging studies to examine whether males and females differ in age-related reduction of specific brain regions involved in spatial memory.
The Yerkes National Primate Research Center of Emory University is one of eight National Primate Research Centers funded by the National Institutes of Health. The Yerkes Research Center is a recognized leader for its biomedical and behavioral studies with nonhuman primates, which provide a critical link between research with small laboratory animals and the clinical trials performed in humans. Yerkes researchers are on the forefront of developing vaccines for AIDS and malaria, and treatments for cocaine addiction and Parkinson's disease. Yerkes researchers also are leading programs to better understand the aging process, pioneer organ transplant procedures and provide safer drugs to organ transplant recipients, determine the behavioral effects of hormone replacement therapy, prevent early onset vision disorders and shed light on human behavioral evolution.