P. M. S.

The acronym that many men fear...

A sudden slew of papers in the last week on the subject of the female hormonal cycle, which all try to explain why some women behave differently prior to their menstrual periods. This is a phenomenon with which hetero men use to explain away what they think of as irrational behaviour in women. And how many have witnessed foolhardy men asking a woman: "You on your period, or what?"?

Silly human behaviour aside, some people take the issue of PMS and its associated behaviour quite seriously:

• Hormonal Cycle Modulates Arousal Circuitry in Women Using Functional Magnetic Resonance Imaging, by Goldstein et al. in the Journal of Neuroscience this week. Their findings? That MRI scans showed an increase in acvitity in the parts of the brain involved in the stress response in the early follicular phase (i.e. start of the menstrual period) when the women were shown unpleasant images. (This was, honestly, quite a yucky paper to read, stuffed to the gills with jargon and completely free of clear statements of facts... In fact, it reminded me of those crappy business-speak articles, and of the Dilbert comic strip. Someone really needs to send up scientists the way Scott Adams has with the cubicle-world...)
• PMS brain, an article about the work of I. Mody at UCLA (I know... add an "o"... You'd be surprised how many scientists have very fitting names for their subject matter... Mine is one too...). This isn't a paper, which makes it SO much easier to read, and more understandable too. OK, I'm a little biased because they do some REAL science here, looking at the different ways neurons fire electrical signals at different parts of the ovarian cycle, and not that hand-waving guesstimation of brain imaging (I'll eat my words soon, no doubt). They found that a receptor in the brain actually changes its subunits (the components of the receptor), which causes changes in intensity of electrical firing in the neurons. While it's not very accurate to compare a rodent's oestrus cycle to a human, this could provide a mechanism for the above finding. The paper's here if anyone's interested.

So, essentially, the cycling hormones can cause changes in brain activity, and as such, lead to behavioural changes. The mechanism proposed by the second paper suggests a reason why different women have different responses to their fluctuating hormones, with some suffering from depression while others become more aggressive. All still pie-in-the-sky though...