Fruit flies unlock secrets of memory
Using fruit flies and strong odors, UH researchers have made significant progress in understanding memory formation and the works of Pavlovian conditioning. The research has revealed important activity in nerve cells as well as interactions with proteins that regulate and control the mechanisms behind forming memories.
The research is headlined by Gregg Roman, an associate professor of biology and biochemistry as well as director of the Biology of Behavior Institute at UH, and Shixing Zhan, his postdoctoral associate. Their findings were published recently in Current Biology, a scientific bimonthly journal published by Cell Press, titled “Presynaptic Inhibition of Gamma Lobe Neurons Is Required for Olfactory Learning in Drosophila.”
Brigitte Dauwalder, the co-vice director of the BoBI, said Roman’s research strongly contributes to the institution’s researching goal.
“BoBI provides an enriched intellectual environment that emphasizes interdisciplinary research and creative approaches to understanding behavior,” Dauwalder said. “This is cutting-edge research published in a top journal. It increases our visibility and demonstrates the high quality of work performed in this department and the University.”
Roman said that within Drosophila — a genus of fruit fly — exist nerve cells called gamma lobe neurons that play a role in olfactory learning, which is a type of Pavlovian conditioning that focuses on the recollection of memories of odors.
“Drosophila readily learn to associate odors with punishments and rewards,” Roman said. “While flies can learn using other sensory modalities, these paradigms and circuits are not as well-defined. We focused on olfactory learning in order to take advantage of the genetic tools and knowledge previously developed for this paradigm.”
According to Roman and Zhang’s research, the gamma lobe neurons are activated by odors, and training the flies to associate an electric shock with an odor changed how the cells responded to odors by developing a modification in the gamma lobe neuron activity, called memory trace. Ultimately, the cells responded more strongly to the trained odor than to the untrained odor.
They also were able to show that a specific protein – the heterotrimeric G(o) protein – was involved in inhibiting gamma lobe neurons. When removing this protein, the gamma lobe neurons resulted in a loss of memory trace and caused poor learning. They could therefore conclude that inhibiting neurotransmitters from the gamma lobe neurons, with the help of the protein, is essential to forming memories.
“By studying the flies, we can get more of an understanding on learning and memory,” Zhan said. “The study can promote our understanding of biological mechanisms of memory and then improve the treatment of memory-related diseases.”
The research even confirms ideas about memories and learning that could aid students during one of the most important weeks of the semester: finals week.
“There are properties of Drosophila learning that we share. When Drosophila, like people, cram or study over long blocks of time without breaks, they do not form long-lasting memories,” Roman said. “Consolidating long-lasting memories requires the lessons to be learned over several short sessions with breaks in between.”
The importance of sleep, another function that is heavily manipulated during finals week, in learning can also be seen with the flies. “When Drosophila undergo sleep deprivation, they learn very poorly and do not remember very well,” Roman said.
Although the research has proven to be significant, it only opens the door for a far-from-finished understanding of memory. Roman says there are many more molecular processes that prove to be just as important as the one they identified, and they plan to investigate these processes, as well as look deeper into the functions of the G(o) protein.