A Harvard researcher has managed to thoroughly confuse a mouse's sexual identity merely by monkeying with its odor-detecting brain circuits.
Mice have two types of olfactory systems, which are located in the nose with projections to the brain: the main one (MOE for main olfactory epithelium) for routine smelling such as food detection, and a second one called the veromonasal system (right and left, respectively in pic). That's the one that picks up on pheromones, the smells of love.
Harvard biologist Catherine Dulac and colleagues wanted to see what would happen if they disrupted these systems. In one set of experiments, the team removed the veromonasal organ (VNO), either via genetic manipulation or destructive virus. The change essentially turned the males bisexual--they mated normally with females but also tried to have sex with males. But if their MOE systems were disabled instead, they lost interest in normal mating with females.
The scientists then tried the same experiments on females. "The results were quite spectacular," said Dulac. The females adopted male-like behaviors, trying to mount both males and other females. "People have always assumed that male and female brains had specific circuits for sex-specific behaviors," said Dulac. But the ease with which their circuits can be re-routed suggests otherwise.
So, are there human implications? Apparently the scientists at Harvard's new transgender clinic thought so. When Dulac presented her findings at Harvard, they found the results "fascinating," saying the data could provide clues as to why people feel like they are males or females--an issue that is separate from sexual preference.