Sex & the Brain

Conventional wisdom about the sexes—and most movies marketed to men under 24—work from the premise that men’s and women’s brains are just fundamentally different. The medical spin on this has been that testosterone, in addition to providing extra oomph for muscles, is a key component in the wiring of the male brain. The male brain is first exposed to testosterone in utero, changing basic brain biology and imposing masculinity. Then during puberty, another wash of testosterone results in distinctly male thoughts—the fodder for all that guns-girls-and-parties cinema—in the previously testosterone-primed brain. Deprive the brain of testosterone at either time and you risk perturbing the sublime development of maleness.

Well, it turns out that life may not be quite that simple—at least for mice. A new study in Nature suggests that the brain pathways for male sexual behavior are also present in female mice, and with those pathways comes the potential for male behavior. Even more intriguing is that the activation of these pathways appears to be regulated by the animal’s sense of smell. Mice, like many other animals, use chemicals known as pheromones to transmit sexual signals, among others. Investigators have recently found that disabling the part of the nose that receives these signals—the vomeronasal organ (VNO)—produces some pretty strange effects on the way a mouse acts out its sex.

Males without a functioning VNO appear to have trouble distinguishing between male and female. They will try to mate with either one and won’t fight other males. This is certainly strange, but our existing model can live with it. Maybe some pheromone turns on those testosterone-sculpted parts of the male brain. No pheromone, no male behavior.

But when female mice don’t have a functioning VNO, even stranger things begin to happen. Like their male counterparts, these mice will try to mount both male and female mice and they engage in the peculiarly male (and particularly attractive) behaviors of butt sniffing and pelvic thrusting. These female mice will also mate in the more traditional way. However, their maternal instincts are altered: they spend less time with their pups and are less aggressive in defending their nests.

What does this mean for us? Well, human mating is a bit more complicated than it is for mice, and our perfumes have far less power over our brains (whatever the beliefs of pushy department-store perfumers). But it may hint that biological gender differences are a bit less hardwired and more flexible than the conventional wisdom suggests. For now, let’s just inhale deeply and say that these studies raise important questions about how far apart Mars and Venus truly are.

So As Not To Stress

Nobody likes stress. Not only can it cause sleepless nights and irritable days, we all suspect, at some level, that it can’t be good for our health. Now we can add another reason to reduce the stress in our lives: It may impair our thinking when we’re older, adding tarnish to the luster of our golden years.
A recent study in the journal Neurology concludes that people who experience chronic psychological distress, such as anxiety or depression, are up to 40 percent more likely to develop mild cognitive impairment (MCI) than people not prone to distress. What is MCI? Well, it’s not dementia, but it does represent a measurable decline in thinking ability and may affect more than 15 percent of the older population. Now before you stress out about being stressed out, take a deep breath and keep reading.
In this study, more than 1,000 older people without any cognitive impairment were evaluated for their tendency to experience distress. This group was then assessed annually (for up to 12 years) for signs of MCI.

The study found that psychological distress did not appear to correlate with age, education, or gender. (It’s nice to know that stress is such an egalitarian problem.) But people with higher distress scores tended to have more depressive symptoms. And those participants with the highest distress score (in the top 10 percent) were 42 percent more likely to develop MCI than people with the lowest scores.
Is all this new? Well, not exactly. People who are prone to chronic distress have been shown to be more likely to develop Alzheimer’s disease. They also are more likely to have their thinking decline at a faster rate.
What this study doesn’t tell us is how chronic distress leads to the development of MCI. The authors of the study have some ideas: Perhaps being prone to chronic distress is one of the earliest signs of having MCI. I find this idea less than appealing, because it suggests that the horse is already out of the barn when it comes to chronic distress and the development of MCI. Fortunately, the authors believe there is a more likely explanation.
Their leading theory is that stress has adverse effects on the parts of our brains that help us form and keep memories. They point out that there is evidence that stress has been shown to reduce our ability to form memories, and that severe stress—like post-traumatic stress disorder—may cause changes in the memory-forming parts of the brain. I find this a far more appealing theory, as it’s based on studies of how our brains work and gives us a chance to "turn things around" by dealing with chronic distress in a positive way.
So for now, let’s focus on what we do know: that reducing the stress in our lives is good for lots of reasons. First off we’re happier, as are the people around us. It’s good for our complexions, probably good for our hearts, and maybe even good for our brains. Don’t sweat the small stuff and don’t let the small niggles become big problems. Whether you exercise, meditate, talk to a therapist, or just spend time on the beach, managing stress is a great investment in your short-term and long-term health.