For most people, fruit flies are just annoying visitors in the kitchen. We don’t usually think about fruit flies learning or fighting over mates, but Michaela Superson ’13, a neuroscience major, and Jeffrey Paer ’15, a biology major, have been looking at these complex behaviors in fruit flies to study brain chemistry and memory.
Superson, who spent the past two semesters working on a senior honors thesis project, was interested in neurotransmitters, chemicals that relay messages between different cells in the brain. In particular, she worked with dopamine, a neurotransmitter associated with pleasure and reward.
“My senior thesis provided an excellent introduction to medical research I may conduct in the future,” said Superson, who plans to go to medical school. “It solidified my love of neuroscience and my desire to pursue medicine.”
Her experimental fruit flies were mutants that produce either too little or too much dopamine. She observed the effects that changes in dopamine can have on courtship behavior, compared to the courtship behavior of “normal” flies. Then, she “rescued” the mutant flies, by adding dopamine or a dopamine inhibitor to restore their dopamine levels to normal.
Paer, who is also interested in a medical career, started out as an assistant for Superson’s thesis project and was soon inspired to start his own research testing memory in fruit flies.
Fruit flies may seem far removed from the people that these students want to help, but research on these creatures has broader implications for the workings of the human brain. “Fruit flies are recognized as excellent model organisms for understanding dopamine in general, including its activities in mammals,” explained Professor of Biology Betsey Dyer, advisor to both Superson and Paer. “And flies are, of course, fascinating in their own right.”
Paer became interested in working with fruit flies as a freshman in Professor Dyer’s “Genetics” class. “He was so focused and persistent that I would often see him still working in the fly lab long after everyone else had gone to dinner,” Dyer recalled. His work with Superson and a combination of different interests soon inspired him to start his own research.
“Music is my passion,” said Paer, who began playing piano at age 4, and since then has played cello, trumpet and several genres of guitar. “My background in music initially inspired me to investigate the effects of music or sound on fruit fly memory.” When he learned that fruit flies can only hear a very limited range of sound—100 to 900 hertz (a unit of frequency)—he constructed a tiny speaker system with the help of professors John Collins and Jason Goodman, and Physics Department Teaching Assistant Anthony Houser.
Paer had read a published study in which male fruit flies were paired in a small, enclosed “fighting arena.” When paired, one male would assume a dominant role and the other would be subordinate. When paired again 30 minutes later, the flies would assume the same roles, indicating that they had retained a memory of their relationship. But after more than 30 minutes, the roles were often switched, indicating that the flies had forgotten their established dominance relationship. Paer constructed his own tiny, enclosed fighting arena, and plays a sound when pairing up aggressive males, to see if playing the sound later can help flies to recall their status for longer than 30 minutes.
“So far, Jeff is getting significant data suggesting that sound indeed is helping the flies to recall their status,” said Dyer. He has found that sound can help fruit flies retain a memory for 40 minutes, and he plans to keep pushing that limit.