When you're laid up with a cold or flu, it's not a virus or bacteria making you feel awful and lethargic—it's your own brain. And it's all in the service of helping you get better, according to two new studies in Nature summed up in the Washington Post. Essentially, the body needs to go into illness-fighting mode with behaviors that are beneficial to knocking back an infection but that run counter to how our bodies normally operate. And in order for that to happen, the brain must "intervene," writes Richard Sima. “It seems like all these symptoms—conserving energy, raising temperature to be able to better fight pathogen, and not eating—is actually very beneficial for the animal and orchestrated by the brain, which I think is really a fabulous phenomenon,” says Harvard scientist Catherine Dulac, author of one of the studies.
People may think it's their immune system making them feel lousy, but it is, in fact, the brain, the studies suggest. Researchers found that if they manipulated certain neurons in the brains of mice, they could make the mice behave as if they were sick even though they weren't. Similarly, if they destroyed these neurons, the mice did not get fevers or slow themselves down when they were actually sick, suggesting the neurons play a vital role in responding to illness. One intriguing part of the research is that it might shed light on people who experience chronic symptoms—think long COVID, for example. It's possible signals from the brain to the body to shut down "may accidentally stay on" for longer than is needed and start causing actual harm, says Anoj Ilanges of the Janelia Research Campus, an author on the second study. Read the full story for more. (Read more discoveries stories.)