Sleep is crucial for multiple physiological functions and is conserved from insects to mammals. Although researchers remain unsure of a single function underlying sleep, one hypothesis is that it is critical to development. Indeed, disruption of sleep leads to developmental issues later in life. Adult Drosophila have been a powerful model for studying sleep and development, but the earliest stages of nervous system elaboration occur prior to adulthood. Now, the Kayser lab has begun to define sleep in Drosophila larvae to further investigate the role of sleep in neural development. The present study analyzes sleep patterns of larvae by tracking larval activity over >20 hours stretches and quantifying periods of behavioral quiescence. Larval quiescence meets the behavioral criteria of mammalian sleep, including sustained inactivity, rapid reversibility, and increased arousal threshold. This project further characterizes larval sleep.
First, I describe the postural changes present within larval sleep. Postural changes are another key feature of sleep, conserved from adult Drosophila to humans. We found that larvae demonstrate a characteristic head retraction in conjunction with quiescence, but this behavior had not been researched extensively. In this study, I look at frequency of postural changes in both short and long bouts of quiescence.
Then, I perform a behavior analysis of the quiescent sequence. I examined 1-second images of the minute preceding and the minute following a quiescent episode, quantified the activity levels over each interval, and plotted the average activity for each second.
Finally, I demonstrate that feeding is a distinct behavioral pattern detected by our MATLAB machine vision software. Second-instar larvae were starved, then given 5-minutes to feed on red yeast-paste while I imaged them. Then, I checked that each larva had red in their gut (to verify that they had been feeding), before proving that none of them showed behavioral quiescence according to our algorithm.
The opportunity to fully immerse myself into the lab has shown me the importance of scientific inquiry. Prior to college, I had naively assumed that medicine meant treating patients. While this is partially true, my time in the Kayser Lab has introduced me to the world of translational research. The abstract concepts that I learned during lectures came to life through the larva at the tip of my forceps, broadening my understanding of both science and medicine. As I apply to medical school, it is difficult now to imagine a future focusing only on clinical practice.