Humans evolved to be both hunters and hunted; although Homo sapiens can take down large prey, our species is also vulnerable to large predators. Now, new research reveals how the human brain switches between these two survival modes.
The answer lies in the hypothalamus, a small structure located deep in the middle of the organ. This ancient region of the brain predates the evolution of vertebrates and so appears in all vertebrate animals; similar brain regions also exist in invertebrates. The hypothalamus is known for performing basic survival tasks, such as regulating body temperature, promoting the release of hormones, regulation of circadian rhythms AND sending hunger signals.
The new study, published Thursday (June 27) in the journal PLOS Biologyfound that the hypothalamus also manages the survival behavior of switching between hunting and hunting.
The hypothalamus has previously been shown to take over this task in other mammals, such as rats. But the new research marks the first time the region has been shown to do so in humans, the study authors wrote in their paper.
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The hypothalamus is small—the size of a pea—and is made up of even smaller nuclei that are too small for brain scanning techniques, such as functional magnetic resonance imaging (fMRI), in imaging.
Researchers used several methods to overcome this problem. One involved determining the pulse of cerebrospinal fluid—a clear fluid that flows around and in the spaces in the brain and spinal cord—and then correcting for this motion in their fMRI data. They also used a type of artificial intelligence it’s called deep learning to detect and classify patterns of activity that might otherwise be too subtle to catch.
The team first had 277 volunteers play a video game in which they had to switch from hunting behavior to escape behavior. The game consisted of a simple arena where participants moved an avatar around. The color of the arena boundaries communicated whether participants should shoot or run from another computerized figure.
The brains of these participants were not scanned, but the researchers studied the volunteers’ actions to create a computer model that could tell when someone was hunting or running.
Then, another 22 participants played the same game inside an fMRI scanner. This type of brain imaging takes an indirect measure of brain activity based on the movement of blood and oxygen through different regions of the brain. When a certain area of the brain is active, the flow of oxygenated blood to that area increases.
For comparison purposes, the same 22 participants also did a task that only involved moving their avatar around the screen, without any particular effort to survive.
The results revealed that the hypothalamus acted as a control center, facilitating the transition between predator and prey behaviors. It did this by communicating with a set of other brain regions, including amygdala, a region known for fear processing, and the ventromedial prefrontal cortex, which is known to be involved in decision-making tasks, including assessing risk in a given situation. This shift involved suppressing the behavior from the previous task.
The hypothalamus continues to coordinate the new behavior after this switch occurs, remaining active throughout the process.
“These findings expand our understanding of the human hypothalamus from a region that regulates our body’s internal states to a region that alters survival behaviors and coordinates strategic survival behaviors,” the authors write.
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