Humans have 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 shows how the human brain switches between these two modes of survival.
The answer lies in the hypothalamus, a small structure deep in the center of the organ. This old brain area is older than the evolution of vertebrates and thus occurs in all vertebrates; similar brain areas also exist in invertebrates. The hypothalamus is known for performing very basic survival tasks, such as regulating body temperature, initiating the release of hormones, regulating circadian rhythms And sending hunger signals.
The new study, published Thursday (June 27) in the journal PLOS Biologydiscovered that the hypothalamus also regulates survival behavior, namely switching between hunting and being hunted.
The hypothalamus has previously been shown to take on this task in other mammals, such as mice. But the new study marks the first time the region has been shown to do this in humans, the study authors wrote in their paper.
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The hypothalamus is small – about the size of a pea – and consists of even smaller nuclei that are too small for brain scanning techniques, such as functional magnetic resonance imaging (fMRI), to visualize.
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 holes in the brain and spinal cord – and then correcting this movement in their fMRI data. They also used a kind artificial intelligence Deep learning is used to detect and classify activity patterns that would otherwise be too subtle to notice.
The team first had 277 volunteers play a video game in which they had to switch from hunting behavior to flight behavior. The game consisted of a simple arena in which participants moved an avatar. The color of the edges of the arena indicated whether the participants had to chase or escape from another computer-controlled figure.
The participants’ brains were not scanned, but the researchers studied the volunteers’ actions to create a computer model that could distinguish between chasing and fleeing.
Next, 22 other participants played the same game in an fMRI scanner. These types of brain scans measure brain activity indirectly based on the movement of blood and oxygen through different brain areas. When a particular area of the brain is active, the flow of oxygen-rich blood to that area increases.
For comparison, the same 22 participants also performed a task in which they merely moved their avatar across the screen, with no real drive to survive.
The results showed that the hypothalamus acted as a control center, facilitating the switch between predator and prey behavior. It did this by communicating with a range of other brain areas, including the amygdalaa region known for processing fear, and the ventromedial prefrontal cortex, known for its involvement in decision-making tasks, including assessing risk in a given situation. This switch involved suppressing the behavior of the previous task.
The hypothalamus continues to coordinate the new behavior after this change has occurred and remains active throughout the process.
“These findings expand our understanding of the human hypothalamus from an area that regulates our internal body states to an area that alters survival behaviors and coordinates strategic survival behaviors,” the authors wrote.
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