Neural mechanisms underlying behavioural choices in drosophila melanogaster

Rose, Saloni (2024). Neural mechanisms underlying behavioural choices in drosophila melanogaster. University of Birmingham. Ph.D.

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Abstract

All animals are confronted with crucial behavioural choices on a daily basis, human and other- wise. These choices can range from the basic decision to feed or rest, to more complex decisions involving social interactions or finding a suitable mate. Behavioural choices are flexible and modulated by an animal’s physiological needs and external environment. Despite the importance of behavioural choices in animal survival, very little is known about the underlying neural mech- anisms that control them. How does the brain evaluate alternative options and determine the appropriate course of action? What influence do internal states, such as hunger or the health status of the animal, have on these pivotal decisions?

In my thesis, I aimed to uncover the neural basis of behavioural choices underlying various con- flicts using Drosophila melanogaster as a model system. Drosophila exhibits a diverse range of innate behaviours such as courtship, feeding and escape, each displaying remarkable stereotypy. Its relatively simple brain structure, coupled with an array of available genetic tools, makes it an ideal model organism to address this question.
In Chapter 2, I delved into the trade-off between reproduction and immunity. Using several bac- terial pathogens, I found that both infected male and female flies prioritised mating over survival suggesting that reproductive behaviours remain preserved despite the metabolic cost of infection.

Chapter 3 focused on the behavioural choice between feeding and courtship in male Drosophila. Starved males showed a preference for initiating feeding before courtship, while well-fed males prioritised courtship. Together with a master’s student in our lab, we identified the tyramine sig- nalling pathway as a key player in this decision-making process. Tyramine serves as a satiety sig- nal, activating courtship-promoting neurons while simultaneously inhibiting feeding-promoting neurons. Conversely, the perception of food inhibits courtship-promoting neurons and activates feeding-promoting neurons. This antagonistic regulation of important neuronal modules enables flies to prioritise one behaviour over the other in a state-dependent manner.

In Chapter 4, I explored the choice between feeding and escape behaviours in flies. I observed that males starved for 24 hours exhibited a preference for escape over feeding. However, this behavioural prioritisation was reversed by the severity of starvation in a sex-specific manner. Em- ploying techniques such as connectomics, neuroanatomy, and behavioural assays, I unravelled the neural mechanisms underlying this critical behavioural choice, specifically connecting sen- sory information to motor output.

These findings advance our understanding of how the brain resolves behavioural conflicts and incorporates the internal state of an animal to elicit the most appropriate behaviour. Through my research, I shed light on the neural mechanisms underlying behavioural choices in various contexts, using Drosophila melanogaster as a powerful model system.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):