Ah, the joys of womanhood. When the female body decides that baby-making time is over, many women experience hot flashes–the occasional onset of skin redness, sweating, increased heart rate and in general feeling like you’ve just been teleported onto the sun’s surface. Yet scientists don’t really know what actually causes women to have hot flashes during menopause, or how the brain responds to them.

A new study from Wayne State University’s medical school tries to get at the latter question through in vivo brain scans of women having hot flashes. The researchers claim it’s the first study to suggest that hot flashes originate in specific brain regions.

While it’s relatively easy to study the way the body responds to external heat stimulation, “hot flashes are unique because they are internally generated, so studying them presents unique challenges,” according to Robert Freedman, the study’s lead investigator and a professor of behavioral neurosciences and psychiatry.

Twenty postmenopausal women who reported experiencing at least six hot flashes a day were put in an fMRI scanner to identify their neural response to the experience. Because having six or more hot flashes a day wasn’t painful enough, the study’s subjects “had to lie in the MRI scanner while being heated between two body-size heating pads for up to two hours while we waited for the onset of a hot flash.” The researchers then measured their sweat levels to determine when the hot flashes actually occurred. Yikes.

They found that before the hot flash even happened, activity spiked in the brain stem region, where thermal regulation may occur. Once the hot flash started, activity increased in the insula and prefrontal cortex. No significant activity was observed in the hypothalamus, a brain region that has been linked to thermoregulation before, a fact the researchers could not explain and note among their limitations.

This staggered brain response could reflect a difference between the origins of hot flashes and our perception of them. The activation of brain stem regions might be where the hot flash begins functionally, then the later activation of regions like the insula and prefrontal cortex reflects the person becoming conscious of the feeling.

The study is online in the journal Cerebral Cortex.