UCI researcher: male, female brains are different 'mosaics'

Women should get angry when they read this story, and men should as well, says Larry Cahill, a neuroscientist at UC Irvine who studies what he considers to be the profound differences between the brains of men and women.

But Cahill, who delivers a talk on his research at UCI on Wednesday, hopes the anger won't come in its usual form: over misguided arguments about whether men or women are more intelligent.

No evidence exists for gender-based, biological impediments to academic achievement, he says – although he thinks there might be biological contributions to success in some fields.

Instead, Cahill hopes to provoke a reassessment among his colleagues, and anger among the general public, about medical science's failure to take gender-based brain differences seriously.

The differences exist at virtually all levels, he says, from those of tiny cells to large structures in the brain, from brain chemistry to what he calls intriguing differences in the way men and women remember emotionally searing events.

And a failure to see the differences can have medical consequences. Men and women react to pain medications differently. They show differences in symptoms of schizophrenia. Chronic stress can damage men's brains but, on average, has far less severe effects on women.

Hormonal differences can affect memory; one of Cahill's students made waves in 2011 when she discovered that taking the pill can cause women's memories of emotional material to more closely resemble those of men.

Virtually any brain disease, Cahill says, comes along with male-female differences big enough to call for major differences in medical treatment.

Cahill's talk begins at 7 a.m. Wednesday at the University Club; register to attend and pay the $35 fee at insideedge.org.

Q. What are some of the big differences emerging between male and female brains?

A. It's not the case that I can sit here and point to anything that is a single, dramatic thing – black and white – that is only in this sex and not the other. As a rule that is not the case. What it is, is just a storm of sex differences, big and little, found all over the place – down to the level of single neurons. We see these differences everywhere, and we started to realize, damn, we simply assume they aren't there. And these sex differences have implications for how the brain works and how to fix brains. That's your big story right there.

For me it's the existence of this huge fire in neuroscience. We've been collectively in kind of denial about it. But we've hit some sort of critical mass in the last couple of years. It's really starting to change.

Q. What differences have you seen that you'll mention in your talk?

A. One is not from the domain of neuroscience, but the domain of heart care. First of all, it turns out the No. 1 killer of women – which might surprise you – is heart attacks. More women die of heart problems than of all cancers combined.

Interestingly, women are much more likely to present the doctor with what are called atypical heart-attack symptoms. It isn't pain in the chest or down the left arm. They might be tired.

But you know why they are considered atypical heart-attack symptoms? Because they're not men. What is defined as typical heart-attack symptoms is defined on the basis of men. They're not atypical heart-attack symptoms if you're a woman. The typical woman is much more likely to go to the typical doctor and not be diagnosed properly.

Q. So what you're finding are not the cliché behavioral differences we might expect, but biological differences?

A. I stay away from the "12 things" that might be found in Vogue magazine. It is the case that male humans and male rats seem to navigate through space differently than female humans and female rats. It turns out that male rats and male humans are more likely to navigate by dead reckoning – knowing which way is north, east, south and west. Female humans are more likely to navigate through landmarks – go up to this 7-11, turn left. There's an intriguing difference right there.

It inevitably leads to the joke: Will male rats stop and ask for directions? The answer is no, because they're males.

Here's another (example): Women are more likely to get clinical depression than men.

To equally treat men and women for heart care, pain, depression, schizophrenia, you have to understand not just how they are similar, but how they are different. So if you treat women just like men, someone is not being treated equally.

Some people start to get real upset at any suggestion of sex differences in brain function. I say, sorry, but my job as a scientist is not to bend my pursuit of truth to accommodate anyone's political concerns. What I say to people when the issue comes up – it doesn't come up very often – I say, "I'm not Galileo, and you're not the Catholic Church."

Q. What are some of the other medical conditions that might require sex-specific treatment?

A. Almost any disease related to the brain that you can think of. We cannot optimally treat women by continuing to pretend they are simply men with pesky sex hormones. It is very, very clear that the brain mechanisms of pain perception are similar in some respects and different in other respects in men and women. Yet attempts to develop pain medications, to my knowledge, pay almost no attention to the differences. Therefore it must be the case that pain medications being developed largely on the basis of male animals are going to be suboptimal on females. It comes to the point where the scales fall off your eyes and you go, "Damn, this is huge."

By the way, every woman reading this article should start to get mad. And every man should while they're at it.

Male and female brains are like two mosaics – very similar in some respects, very different in others. It's not as simple as Mars and Venus.

Contact the writer: 714-796-7865 or pbrennan@ocregister.com.

• GRAPHIC: Inside the brain