Joining Snowdon in working with the marmosets were Toni Ziegler, Nancy Schultz-Darken and Pam Tannenbaum of the Wisconsin National Primate Research Center at UW-Madison. The Primate Center provided four male marmosets for the study. The researchers trained and transported them from the University of Wisconsin to the University of Minnesota, where the imaging took place.
The researchers imaged the male marmosets' neural activity while they were presented with anogenital gland secretion samples from periovulatory females, those at or close to ovulation. Other samples, taken from ovariectomized females, gave the researchers a way to compare how the males responded to female marmoset scents containing no sexual cues, according to Ziegler. When the same males smelled the "sexier scents" from the ovulating females, the scientists could discern which neural areas showed further activation, thus identifying areas where information processing occurs.
"We were surprised to learn how great a role the neural areas related to cognitive processing play in determining how males respond to sexually receptive females," Ziegler says.
To preempt stress to the animals, Ziegler and Schultz-Darken brought the marmosets' cage-mates along on the road trip. "The marmosets were trained in advance, over brief periods, to get used to a mock imaging process," Ziegler says. "By the time they underwent the real thing, they did not exhibit any signs of stress."
"We acted as advocates for the marmosets," adds Schultz-Darken, who is also a colony manager at the Primate Center. "It was very important to properly habituate them to the imaging equipment. We had a wonderful experience with the facility and the people at the University of Minnesota."