Circuits for Looming Feature Integration in Drosophila
Wednesday, August 25, 2021
1:00 PM-3:00 PM
BIOMED PhD Research Proposal
Title:
Circuits for Looming Feature Integration in Drosophila
Speaker:
HyoJong Jang, PhD Candidate
School of Biomedical Engineering, Science and Health Systems
Drexel University
Advisor:
Catherine von Reyn, PhD
Assistant Professor
School of Biomedical Engineering, Science and Health Systems
Drexel University
Details:
Animals must generate relevant behaviors in response to their environment that are essential for survival. The relevant behavior should be matched appropriately to a rapidly changing environment. To accomplish this goal, an animal’s brain must acquire and process sensory input from the environment and then integrate this information to select and drive an appropriate behavior. However, the underlying mechanisms behind these sensory to motor transformations are not well understood as the neural circuits that bridge complex sensory inputs and relevant behavior outputs are largely incomplete.
We use the fruit fly Drosophila melanogaster as our model organism to investigate sensorimotor transformations. In doing so we have great leverage to study underlying mechanisms at the level of individual neurons and small neural circuits. Approximately 60% of genes in humans have a homolog in the fly and many cellular mechanisms are well conserved. Additionally although the fruit fly has numerical simplicity in the number of neurons compared to humans, it still has a richness in its behavior. Finally, in the fruit fly we have powerful genetic toolkits that enable direct access to individual neurons within a circuit.
We investigate sensorimotor circuits that drive escape behaviors to “looming” stimuli that mimic a object approaching on a direct collision course. Escape is one of the most explored animal behaviors since the behavioral principles are conserved across species due to its essential need for survival and the behavior is easily reproducible in a laboratory setting. Prior research has demonstrated that loom-encoding neural responses are similar across species from vertebrates to invertebrates. In response to looming stimuli, animals can perform a variety of escape behaviors such as freezing, fleeing, jumping, and flight initiation. This flexibility was thought to emerge from parallel sensorimotor pathways that compete to select a behavior. However, only a few of these potential pathways have been identified. Our preliminary data and recent data from other labs suggest at least five looming-evoked escape pathways may exist in the fly. Each pathway consists of a pair of descending neurons (DNs) that are thought to be a critical bottleneck in the flow of information from sensory systems in the brain to motor circuits in the ventral nerve cord (VNC, fly “spinal cord”). Additionally, our preliminary analysis using the recent electron microscopy (EM) connectome of the fly brain demonstrates looming responsive DNs are highly interconnected in the brain. These data suggest interactions between pathways further shape sensorimotor integration to select and drive a relevant escape behavior.
We seek to understand how looming visual information is integrated across multiple DNs and how DNs interact with each other to generate a relevant escape output. In Aim 1 we determine key looming responsive DNs by developing a projection system for displaying looming stimuli while performing in-vivo whole-cell electrophysiology on behaving, tethered flies. In Aim 2 we investigate the mechanisms for bilateral looming integration in an essential escape DN (DNp01) by discovering a key commissural interneuron in the escape circuit. Finally, in Aim 3 we investigate how looming visual information is further shaped by DN to DN interactions across the escape circuit. In sum our results will enhance the current understanding of how multiple sensorimotor pathways interact with each other to integrate behaviorally relevant visual information in parallel. As neurons homologous to DNs play a key role in animal behavior this proposal also provides insight into the general mechanisms for sensorimotor integration across species.
Contact Information
Natalia Broz
njb33@drexel.edu