Unraveling the Neurological Underpinnings of Fear: Study Discovers Eye-Aversion Mechanism in Fruit Flies

by Hiroshi Tanaka
Neurological mechanism of fear

Scientists from the University of Tokyo have discovered a set of neurons in the brains of fruit flies that regulate the visual aversion response to perceived threats. This breakthrough potentially sheds light on the human response to fear, with the research team setting their sights on further exploring this neural network. Their work may eventually contribute to the development of treatments for anxiety disorders and phobias.

They discovered a specific neuronal cluster in fruit fly brains that governs visual aversion to frightening stimuli.

The researchers at the University of Tokyo discovered that we might avert our gaze from fear-inducing objects due to a specific group of neurons located in the visual region of the brain. They found that these neurons, found in fruit fly brains, discharge a chemical named tachykinin, which appears to direct the flies’ movement away from a possible threat. As fruit fly brains provide a handy model for larger mammals, this research could enlighten us on human reactions to fear and phobias. The next step for the team is to understand how these neurons interact within the wider brain network, potentially revealing how vision is controlled by fear.

Does the sight of a creepy-crawly spider send you into a frenzy, or do horror movies make you cover your eyes? Shunning scary sights is a universal experience among humans and animals alike. The researchers have posited that this might be due to a group of neurons in the brain that manage vision when fear is triggered.

In tests, calm fruit flies showed no change in behavior towards a visual object, but when scared, they scampered away. Credit: 2023, Tsuji et al.

“We’ve unearthed a neural mechanism where fear modulates visual aversion in fruit fly brains. It appears that a single cluster of about 20-30 neurons controls vision during a fearful state. As fear affects vision across species, including humans, this mechanism could also be at play in human brains,” elucidated Assistant Professor Masato Tsuji from the University of Tokyo’s Department of Biological Sciences.

The researchers simulated a physical threat using air puffs, observing that the flies quickened their pace after exposure. If given a choice, the flies avoided the path with air puffs, implying that they perceived them as a threat. Next, a small black object, about the size of a spider, was placed 60 degrees to the right or left of the fly. The object alone didn’t alter behavior, but when paired with air puffs, the flies evaded the object and shifted so it was behind them.

To decode the molecular mechanism behind this aversion, the team manipulated the activity of specific neurons in genetically modified flies. While these flies retained their vision and motor functions, and still avoided the air puffs, their fear response was altered, resulting in a lack of visual avoidance of the object.

Tsuji noted, “We inferred that the tachykinin-releasing neuron cluster was essential for triggering visual aversion. When we monitored the flies’ neural activity, we were surprised to see it occurred in an oscillatory pattern. This oscillatory activity is particularly rare in fruit flies and was previously undetectable due to technological limitations.”

Through the use of genetically encoded calcium indicators, the researchers could observe the fly neurons lighting up when activated. Modern imaging techniques revealed the changing, wave-like pattern of light, which was previously missed.

Going forward, the team aims to understand how these neurons interact with the broader brain network. Even though these neurons are situated in a known visual region of the brain, it is still unclear how they communicate with the rest of the brain to regulate visual escape from perceived threats.

“Our next mission is to unravel the process of visual information transmission within the brain, so we can ultimately map out how fear controls vision,” stated Tsuji. “Our discovery might someday provide valuable insights for treating psychiatric disorders resulting from excessive fear, such as anxiety disorders and phobias.”

The findings of this research, entitled “Threat gates visual aversion via theta activity in Tachykinergic neurons,” were published in Nature Communications on 13 July 2023. The study was supported by several foundations and organizations, including the Japan Society for the Promotion of Science (JSPS), MEXT Grants-in-Aid for Scientific Research on Innovative Areas, and the Uehara Memorial Foundation.

Frequently Asked Questions (FAQs) about Neurological mechanism of fear

What did the team of scientists from the University of Tokyo discover in their research?

The scientists identified a specific group of neurons in the brains of fruit flies that are responsible for visual aversion to perceived threats. This finding could potentially provide insights into how humans react to fear.

How does the discovered group of neurons affect the behavior of fruit flies?

These neurons release a chemical called tachykinin that appears to control the fly’s movement to avoid facing a potential threat. The flies react to a simulated threat (puffs of air) by increasing their walking speed and choosing a path without the threat.

Can these findings be applicable to humans?

Yes, the researchers believe that since fear affects vision across animal species, including humans, the mechanism they found in fruit flies may also be active in humans.

What are the implications of this research for the treatment of anxiety disorders and phobias?

The research team aims to explore this brain circuitry further and to map out how fear controls vision. Their findings might someday provide valuable insights for the development of treatments for psychiatric disorders resulting from excessive fear, such as anxiety disorders and phobias.

What are the next steps in this research?

The researchers plan to understand how these neurons fit into the broader circuitry of the brain. They are particularly interested in figuring out from where these neurons receive inputs and to where they transmit them, to regulate visual escape from objects perceived as dangerous.

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RobScienceFan July 13, 2023 - 5:02 pm

Kudos to the Tokyo team. Interesting insights on fear responses in fruit flies, can’t wait to see how this relates to humans, if it does. Keep it up guys!

LindaM July 13, 2023 - 8:06 pm

wow! really interesting research. who would’ve thought we could learn so much about fear from tiny fruit flies!

FruitFlyFreddy July 13, 2023 - 8:15 pm

fruit flies doin it again!! simple organisms leading to complex understanding… science is cool man.

Dan_the_NeuroNerd July 13, 2023 - 9:52 pm

This kind of research fascinates me! The neurological connection between fear and vision… it’s more complex than we think, huh?

TerrifiedTerry July 14, 2023 - 1:15 am

so thats why i close my eyes during horror movies? lol, good to know its not just me.

NervousNelly July 14, 2023 - 8:26 am

Interesting, if this leads to better treatment for anxiety disorders, it would be a real game changer. Fingers crossed!


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