Female Brains Are More Active?

By Neuroskeptic | August 8, 2017 2:52 pm

Another day, another over-hyped sex differences neuroscience study. The headlines this time around are especially cringeworthy:

Study Finds Women’s Brains Are Far More Active Than Men’s

Women Are Using A LOT More Of Their Brains Than Men. Surprise, surprise 😏

Women really DO overthink things! Scans reveal they have ‘more active brains than men’

The paper in question was published in the Journal of Alzheimer’s Disease and it comes from a group led by Dr. Daniel Amen. Amen is a controversial psychiatrist who claims to be able to diagnose and treat mental illness with the help of a brain scanning technique called SPECT. SPECT is not widely accepted for this purpose.

Personally, I think Amen’s SPECT psychiatry is dangerous and unscientific. However, to be fair, Amen is in a good position to study sex differences using SPECT. His “Amen Clinics” have carried out tens of thousands of SPECT scans, meaning that Amen probably has more of this kind of data than anyone else in the world.

And, to be fair, the new paper is actually pretty solid. Amen et al. found a convincing sex difference in brain blood flow as measured using SPECT, in 119 healthy subjects and a whopping 26,683 Amen Clinic patients. Across most of the brain, women on average had higher blood flow than men:

amen-male-female

The sex difference was modest in size. For total brain blood flow, the effect size Cohen’s d was 0.34 at baseline, and d = 0.37 in participants performing a cognitive task. In healthy controls, the whole-brain differences were larger: d = 0.65 baseline and d = 0.55 task. A Cohen’s d of 0.5 is conventionally considered a “moderate” difference.

So the difference wasn’t huge, but given the enormous sample size in this study, it seems robust. However, it’s important to remember that this was a study of blood flow, not of brain activity.

These results do not mean that women’s brains are more active, or that women use more of their brains, or that they’re prone to “overthinking”. The results simply don’t tell us that. All we know is that more blood flows through blood vessels in the female brain. There could be many possible explanations for this.

In fact, to me, the results suggest that the sex difference may be a basic physiological one, rather than a reflection of different patterns of brain activity. If women’s brains were carrying out more activity at baseline (“overthinking”), you’d expect the sex difference to be smaller during a cognitive task, on the grounds that neither males nor females would be at baseline in this condition. In fact, the sex difference was if anything larger during the cognitive task.

Overall, this is a surprisingly good paper given its provenance, but don’t believe the headlines.

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  • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

    more blood flows through blood vessels in the female brain” I’ve been with my woman for 27 years. Damned if I know what goes on in there.

    The natural and proper ratio of males to females in tasks of creative, intensive, and extended endeavor is the empirical ratio of males to females in felony imprisonment – sweating, swearing, lusting, hairy, ugly, violent, and driven. It’s a comfortable place to be when getting things done (admittedly on the reflex side of the bell curve).

    • TLongmire

      Can’t help but see trama in the far right one

  • TLongmire

    The increased blood flow is experienced as bodily sensations. The area of the brain with increased blood flow is producing vasodilators that are in a feedback cycle with areas of the body. Honest people experimenting with biofeedback could figure that out quickly.

  • Paul Rain

    Any norming to brain size?

    Wouldn’t be surprising that a group with a generally smaller version of an organ, would have it more active when it’s just ticking over.

  • smut clyde

    My first thought was to wonder about brain size as a confound. If absolute mean blood flow has no sex difference, but the values in the calculations were normalised to brain volume (see Paul Rain’s comment), this would be a problem.

    • http://blogs.discovermagazine.com/neuroskeptic/ Neuroskeptic

      I thought that too. But women are smaller than men in every way AFAIK. They have smaller hearts, less blood, on average. So wouldn’t all the differences cancel out when it came to blood flow?

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  • C’est la même

    Isn’t this just another way of spinning the fact that brain imaging studies consistently fail to distinguish gender with high specificity/sensitivity (ROC curve)?

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  • Sys Best

    Did they use brain normalization? Different male/female templates?

  • Sys Best

    From their abstract, first line “Studies have reported that females have widespread increases in regional cerebral blood flow, but the studies were relatively small and inconsistent.” Not at all clear what they mean, I assume higher rCBF compared to males.

    Why do you say this is a good paper? I know you added “given …”, but a good paper is a good paper, shouldn’t be related to provenance.

    BTW, it looks like we know these facts for over 25 years.

    Schizophr Bull. 1990;16(2):247-54.
    Gender differences in regional cerebral blood flow.
    Gur RE, Gur RC.

    University of Pennsylvania, Brain Behavior Laboratory, Philadelphia 19104.

    Abstract

    Gender differences have been noted in neurobehavioral studies. The 133xenon inhalation method for measuring regional cerebral blood flow (rCBF) can contribute to the understanding of the neural basis of gender differences in brain function. Few studies have examined gender differences in rCBF. In studies of normal subjects, women have higher rates of CBF than men, and this is related to age. Usually by the sixth decade men and women have similar flow rates. Fewer studies on rCBF in schizophrenia have examined sex differences. The pattern of higher flows for females maintains, but its correlates with gender differences in clinical as well as other parameters of brain function remain to be examined.

  • Sys Best

    J Am Coll Cardiol. 1999 Feb;33(2):463-70.

    Gender differences in myocardial blood flow dynamics: lipid profile and hemodynamic effects.

    Duvernoy CS, Meyer C, Seifert-Klauss V, Dayanikli F, Matsunari I, Rattenhuber J, Höss C, Graeff H, Schwaiger M.

    Klinik und Poliklinik, Munich, Germany.

    Abstract

    OBJECTIVES:

    The purpose of the study was to compare myocardial blood flow (MBF) in hyperlipidemic postmenopausal women and age-matched hyperlipidemic men, and to analyze the relationship between cholesterol subfractions and myocardial blood flow in men and women.

    BACKGROUND:

    Women are protected from coronary artery disease (CAD) events until well after menopause, in part due to gender-specific differences in lipid profiles.

    METHODS:

    To examine the effect of these influences on coronary microcirculation, MBF was quantitated with N-13 ammonia/PET (positron emission tomography) at rest and during adenosine hyperemia in 15 women and 15 men, all nondiabetic, who were matched for age and total cholesterol levels (53+/-4 vs. 50+/-8 years, p = NS, 6.44+/-1.1 vs. 6.31+/-0.85 mmol/liter, or 249+/-41 vs. 244+/-33 mg/dl, p = NS).

    RESULTS:

    Women had significantly higher high density lipoprotein (HDL) and lower triglyceride (Tg) levels than did men, and they showed significantly higher resting MBF and stress MBF levels. Significant correlations were found between resting and hyperemic MBF and HDL and Tg levels (r = 0.44, p < 0.02 for stress MBF vs. HDL; r = 0.48, p < 0.007 for stress MBF vs. Tg). Gender was the strongest predictor of hyperemic MBF in multivariate analysis. Women responded to adenosine hyperemia with a significantly higher heart rate than did men, and hemodynamic factors correlated significantly with blood flow both at rest and during stress.

    CONCLUSIONS:

    These data suggest that the favorable lipid profile seen in women may be associated with preserved maximal blood flow in the myocardium.

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  • liseeliot

    probably an artifact of brain size: bigger brains have less gray matter relative to smaller brains and gray matter is more metabolically active than white matter

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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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