Predator or prey? This 'switch' in the brain toggles when you're hunting or being hunted

Humans evolved to be both hunters and hunted; although Homo sapiens can take down large prey, our species is also vulnerable to big predators. Now, new research reveals how the human brain switches between these two modes of survival. 

The answer lies in the hypothalamus, a tiny structure nestled deep in the middle of the organ. This ancient brain region predates the evolution of vertebrates and thus appears in all vertebrate animals; similar brain regions also exist in invertebrates. The hypothalamus is known for performing very basic survival tasks, such as regulating body temperature, triggering the release of hormones, regulating circadian rhythms and sending out hunger cues. 

The new study, published Thursday (June 27) in the journal PLOS Biology, found that the hypothalamus also manages the survival behavior of switching between hunting and being hunted. 

The hypothalamus had previously been shown to take on this task in other maMMAls, such as mice. But the new research marks the first time the region has been shown to do so in humans, as well, the study authors wrote in their paper.

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The hypothalamus is small — about the size of a pea — and it's made up of even smaller nuclei that are too tiny for brain scanning techniques, such as functional magnetic resonance imaging (fMRI), to image. 

The researchers used several methods to overcome this problem. One involved determining the pulse of cerebrospinal fluid — a clear fluid that flows around and into gaps in the brain and spinal cord — and then correcting for this motion in their fMRI data. They also used a type of artificial intelligence called deep learning to detect and classify activity patterns that might otherwise be too subtle to catch.