According to a team of scientists from UW-Madison and other universities, male marmosets, small tree-dwelling monkeys from Brazil, are not ruled only by sexual arousal but use parts of their brain associated with higher-level cognitive processes to choose a mate.
\We have this stereotype of male mammals, including humans, being driven by their gonads,"" said Charles T. Snowdon, a UW-Madison professor of psychology who helped direct the study.
Toni Ziegler, Nancy Schultz-Darken and Pam Tannenbaum of the Wisconsin National Primate Research Center at UW-Madison trained the four male marmosets before transporting them to the University of Minnesota. There, they used a functional magnetic resonance imaging device, which charts oxygen consumption over time, and thus activity, in a cross-section of the brain. A colored display shows researchers what areas of the brain are most active. The marmosets smelled the scents of both sexually receptive and non-receptive females while in the magnetic tubes.
""In humans, the stimulus is usually visual ... erotic films or whatever,"" Schultz-Darken said. ""Marmosets are much more scent-driven.""
The team originally intended to test the viability of the imaging technology for brain studies by looking at sexual arousal, but with fMRI, Snowdon said, ""We don't just have to look at one area of the brain.""
The ability to find unexpected activity in ""thinking"" sections of the marmosets' brains is just one benefit of the technology over previous techniques.
""This is in lieu of having to do some sort of surgery,"" Ziegler said.
Before they could non-invasively monitor brain activity, scientists had to see what behaviors animals lost when certain portions of their brain were missing, she said. In this study, she said, the marmosets were monitored to ensure they were not even distressed.
This study's success opens new possibilities in brain research, Snowdon said, especially since researchers can control the marmosets' development and social situations, while human subjects are influenced by their lives outside the lab.
Marmosets were chosen for the study because their social and family structure is similar to that of humans and they are small enough to fit into more powerful fMRI tubes, Schultz-Darken said.
In addition, she said, ""They're just nice. They're great animals to work with.""
The study appears in the February 2004 issue of the Journal of Magnetic Resonance Imaging.
