(CN) — The next time you see a fruit fly buzzing around, remember that there’s a lot more going on in its tiny brain than meets the eye — especially when love, or at least mating, is on the line.
Male fruit flies are so driven to find a mate that they’ll ignore danger, even when a predator is nearby, according to researchers from the University of Birmingham in England in a study, published Wednesday in Nature. The researchers say that as these tiny insects get closer to mating, they become almost blind to threats, all thanks to a brain chemical called dopamine.
The researchers, led by Carolina Rezaval of the university’s school of biosciences, found that when a male fruit fly is in the thick of courting a female, his brain starts to tune out everything else.
“Every day we make decisions that require us to balance opportunities and risk — but we know little about what is happening in our brains as we make these choices,” Rezaval said in a statement. “By studying the neural pathways that are activated in the brains of fruit flies, we can find out more about these processes. As the fly pursues his courtship and is close to mating, we can clearly see that when a threat is introduced, he simply does not see it.”
In their experiment, the team used advanced imaging techniques, like two-photon microscopy, to peek inside the flies’ brains during courtship. They even introduced an artificial “threat”, using light and shadow to simulate a predator flying nearby, just to see how the flies would react.
At the start of the courtship, the male flies noticed the danger and backed off.
“During earlier stages of courtship, we found the presence of threat triggered certain visual neurons in the brain that interfere with neurons governed by serotonin,” said co-author Laurie Cazale-Debat. “This prompts flies to abandon their courtship and escape the threat.”
But as the courtship progressed and the male fly got closer to his goal of mating, something changed.
The dopamine levels in his brain began to rise, and this chemical boost started blocking out the sensory pathways that normally help him detect danger.
“As the courtship advances, however, the increase in dopamine blocks key sensory pathways, reducing the ability of the fly to respond to threat and causing it to focus on mating,” Cazale-Debat added in a statement. “The animal must decide what is most important.”
According to researchers, this phenomenon draws an interesting parallel to human behavior. Lisa Scheunemann, of Freie Universität Berlin, compared the flies’ behavior to a scenario many people might recognize.
“Imagine you’re climbing a mountain and you’re close to the summit,” Scheunemann said in a statement. “If the weather changes and conditions become dangerous you might disregard that threat because you are so close to your goal.”
In the case of the fruit flies, the “summit” is successful mating, and they’re willing to ignore almost anything to reach it.
“Our study shows that as courtship progresses, dopamine increases, acting as a sensory filter that blocks distractions and helps the animal focus on the task at hand when close to its goal,” Rezaval said. “We are excited to explore if this is a general decision-making mechanism that is also present in mammals, including humans.”