The findings provide strong evidence that male sexual behavior is hard wired into the female mouse brain and suggests, more broadly, that male and female courtship behaviors exist in the brains of both sexes and are switched on or off by the chemical cues mice use to initiate sex.

"The female behaves exactly like the male," said Dulac. "In the big picture, it suggests that the female brain has a perfectly functional male behavioral circuit."

"People who observe animal behavior have been struck by the fact that the biggest differences in behavior between animals of a given species are gender based," Dulac explained, but little is known about the underlying differences in the brain that govern the characteristic patterns of gender-based behavior.

Scientists have explored many avenues to explain sexually dimorphic behavior. To try and ferret out its cause, they've looked at everything from the influences of hormones such as testosterone to anatomy, positing that there may be a region of the brain that organizes gender-based behavior.

The sensory-controlled neural switch that governs the circuit is most likely different in male and female mice, Dulac noted, but that may be the extent of gender differences in the brain.

The work of Dulac and her colleagues promises to open a new window to the neural mechanisms that underlie gender-based behavior in animals by bringing the senses and an animal's ability to process what it sees, hears, and smells into the equation.

What occurs in humans and other animals may be quite different, Dulac noted, because the mouse depends largely on pheromones and its sense of smell, while humans and many other animals respond more to visual cues or a combination of sensory cues.

Scientists have been studying the vomeronasal organ for a century and
'"/>

Contact: Jennifer Michalowski
michalow@hhmi.org
301-215-8576
Howard Hughes Medical Institute
5-Aug-2007