Women Are Better Connected… Neurally

By Neuroskeptic | April 1, 2011 6:50 am

The search for differences between the brains of men and women has a long and rather confusing history. Any structural differences are small, and their significance is controversial. The one rock-solid finding is that men’s brains are slightly bigger on average. Then again, men are slightly bigger on average in general.

A new paper just out from Tomasi and Volkow (of cell-phones-affect-brain fame) offers, on the face of it, extremely strong evidence for a gender difference in the brain, not in structure but in function: Gender Differences in Brain Functional Connectivity Density.

Here’s the headline pic:
They used resting-state “functional connectivity” (though see here for why this term may be misleading) fMRI in men and women. This essentially means that they put people in the MRI scanner, told them to just lie there and relax, and measured the degree to which activity in different parts of the brain was correlated to activity in every other part. They had a whopping 561 brains in total, though they didn’t scan everyone themselves: they downloaded the data from here.

As you can see the results were highly consistent around the world. In both men and women, the main “connectivity hub” was an area called the ventral precuneus. This is interesting in itself although not a new finding as the precuneus has long been known to be involved in resting-state networks. However, the degree of connectivity was higher in women than in men 14% higher, in fact.

The method they used, which they’ve dubbed “Local Functional Connectivity Density Mapping“, is apparantly a fast way of calculating the degree to which each part of the brain is functionally related to each other part.

You could do this by taking every single voxel and correlating it with every other voxel, for every single person, but this would take forever unless you had a supercomputer. LFCDM is, they say, a short-cut. I’m not really qualified to judge whether it’s a valid one, but it looks solid.

Also, men’s brains were on average bigger, but interestingly they show that women had, relative to brain size, more grey matter than men. Here’s the data (I’m not sure about the color scheme…)

So what does the functional connectivity finding mean? It could mean anything, or nothing. You could interpret the highly interconnected female brain as an explanation for why women are more holistic, better at multi-tasking, and more in touch with their emotions than men with their fragmented faculties. Or whatever.

Or you could say, that that’s sexist rubbish, and all this means is that men and women on average are thinking about different things when they lie in MRI scanners. We already know that resting-state functional connectivity centred on the precuneus is suppressed whenever your attention is directed towards an external “task”.

That’s not a fault of this research, which is excellent as far as it goes and certainly raises lots of interesting questions about functional connectivity. But we don’t know what it means quite yet.

ResearchBlogging.orgTomasi D, & Volkow ND (2011). Gender differences in brain functional connectivity density. Human brain mapping PMID: 21425398

CATEGORIZED UNDER: fMRI, neurofetish, papers
  • http://www.blogger.com/profile/06683483030413488309 Judith Weingarten

    The men weren't resting; they were thinking about sex. (Apologies!)

  • Anonymous

    FYI: Broken link to the brain data!

  • http://www.blogger.com/profile/08475650963396841115 JMG

    “You…interpret the highly interconnected female brain as an explanation for why women are more holistic, better at multi-tasking, and more in touch with their emotions than men with their fragmented faculties…”

    You've just written dozens of headlines citing this article for major news publications. No tough research required!

  • http://www.blogger.com/profile/06647064768789308157 Neuroskeptic

    anonymous: Cheers, fixed.

    JMG: This story doesn't seem to have made the headlines yet; I guess they didn't put out a sufficiently simplistic press-release…

  • Anonymous

    I think comparison between a human society and brain can be useful here. In order to perform a complex task, you can construct a society with expert separate modules (hubs) and less interaction between them. As well, you can design a society with less modular characteristics and more connectivities.These two networks might work in same manner in most of the tasks, but you can presume existence of tasks in which one the networks outperform the other: “You…interpret the highly interconnected female brain as an explanation for why women are more holistic, better at multi-tasking, and more in touch with their emotions than men with their fragmented faculties…” Isn't it sensible?

  • http://www.blogger.com/profile/06647064768789308157 Neuroskeptic

    Oh sure, it's quite possible, but we can't infer that from these data, because it might be something less interesting. Or something equally interesting but different.

  • Anonymous

    Interesting finding – but like you said, it's not clear what to make of it. It is pretty neat though that they were able to replicate their own findings across different samples of women.

    And to me, that makes it better than most of the papers I read in in this area (mostly in psychiatry) that detail a study where they scan some X number of people with some disorder and then claim they differ from controls on some brain region/gene/protein/or some other random biological buzzword of the day.

  • http://www.blogger.com/profile/15705565128439299346 Bradley Voytek

    I have to say I'm pretty surprised that Nora Volkow wrote this, given her recent paper showing how fMRI EPI gradients affect cerebral glucose metabolism:

    I honestly think that that kind of research calls into question a lot of the resting state work…

  • Larsen

    Isn't the difference in brain size between women and men in correlation with the difference in body mass? That, at least, is the explanation I heard for men having, on average, a bigger brain size.

    • JKG

      Men’s bigger body only accounts for 30 percent difference in brain size. After taking that into account men’s brains are on average still 11 percent bigger in total, but only 4 percent bigger in cortical size (area for thinking).

      However bigger brains correlate only 24 percent with intelligence and explain only 9 percent variance in individual IQ scores. So essentially bigger brain may play a part in intelligence (perhaps more visual memory capacity?) but definitely not all, and certainly cannot be used to generalize gender intelligence.

  • http://www.blogger.com/profile/06647064768789308157 Neuroskeptic

    Bradley: Interesting point, I hadn't seen that paper actually, thanks for the tipoff, definately an important issue…



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Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.


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