How dopamine in fruit flies controls their courtship behavior, ignoring threats, and focusing on mating – new research reveals surprising facts about their brain

Male fruit flies exhibit a fascinating pattern of behavior in which they completely ignore threats when engaging in courtship and mating rituals. Research from the University of Birmingham revealed that these flies, driven by the desire to mate, stop reacting to environmental threats. While they can recognize potential threats in the early stages of courtship, as mating approaches, their attention becomes solely focused on females. This phenomenon is primarily associated with a sudden increase in dopamine levels in the flies' brains, which blocks their sensory pathways that would otherwise be responsible for detecting danger.

Neurobiological research shows that dopamine plays a crucial role in these changes in perception in fruit flies. Using advanced imaging techniques, such as two-photon microscopy, scientists tracked neuronal activity in flies during courtship stages. When they created an artificial threat, such as a simulated predator, the flies quickly responded with escape behavior during the early stages of courtship. However, as mating approached, their ability to recognize danger diminished, and dopamine took on a dominant role in decision-making.

This phenomenon is not unique to fruit flies. A similar mechanism could potentially apply to other animal species, including humans. Researchers suggest that it is a universal motivational mechanism, where dopamine, also known as the happiness hormone, acts as a sort of filter that blocks all external distracting factors as we approach a goal. For example, a hiker near the summit of a mountain might not notice changes in weather conditions or other dangers because they are so focused on reaching their goal.

Lead researcher Dr. Carolina Rezaval explained how dopamine plays a key role in how the brain balances reward and risk. In the early stages, when the reward is distant, the fly's brain still pays attention to threats. However, as mating gets closer, dopamine activates neural pathways that reduce sensitivity to threats, allowing the fly to focus exclusively on mating.

The experiment also showed that certain neurons in the fly brain, associated with serotonin, play a role in the early stages of courtship. During these stages, when a threat is present, serotonin helps the flies assess risks and temporarily halt courtship to avoid danger. However, as dopamine takes over, its increased levels block serotonin functions, and the flies become unaware of potential threats.

This discovery could have broader implications for understanding decision-making across different species. Dopamine, the neurotransmitter responsible for the feeling of reward, may play a similar role in mammals and even humans, in situations where risks and rewards are balanced. While many animal species rely on survival instincts when faced with a threat, fruit flies have shown that, when it comes to mating, they prioritize reproductive success over survival.

Researchers used sophisticated technologies like two-photon microscopy to track which neurons in the brain were activated during courtship. Through this technique, they were able to observe how different neural pathways are activated as the fruit fly approaches mating. In the early stages, sensory neurons responsible for detecting threats, such as shadows simulating a predator, would quickly trigger an escape response. However, as courtship progresses, there are drastic changes in brain activity, with dopamine taking a central role, blocking sensory neurons and focusing attention solely on the female.

The research findings reveal much about how the brains of fruit flies make decisions regarding survival and reproduction. Scientists believe that similar mechanisms could be present in many other animal species, including humans. Dopamine is already known for its role in motivation in humans, and this research further confirms its crucial role in decision-making under pressure.

This research, conducted in collaboration with several prestigious universities, including Freie Universität Berlin and the University of Sheffield, provides new insights into how the brain balances reward and risk. Funded by the European Research Council and the Wellcome Trust, this research raises new questions about how different species make decisions in the context of survival and reproduction. Through further research, scientists plan to explore whether this mechanism is present in other species, including mammals and even humans.

Source: University of Birmingham