Details

Vortragende Person/Vortragende Personen:
Dr. Frederic Roemschied, Murthy Lab (Princeton) / University of Cologne

How do nervous systems control social behavior? How flexible is innate social behavior?
During my postdoc with Mala Murthy at Princeton University, I addressed these questions using courtship behavior of the male fly Drosophila melanogaster as a model system. During courtship, the male fly advertises himself to the female using an acoustic signal (‘song’) that is produced via wing vibrations. The female provides sensory feedback to the male in response to his song (e.g. slowing down to an attractive song), which the male uses to update his subsequent song behavior. While previous work used the powerful genetic tools available in Drosophila to identify several neuron types contributing to song production, we lacked an understanding of how these neurons interact to drive song output. The first part of my talk will cover a recent manuscript in which we attempted to close this gap, showing how the previously identified neurons in the male interact at the circuit level to produce adequate song behavior in two different social contexts (abstract below). In the second part of my talk, I will present results from an upcoming manuscript that challenge the prevailing notion that innate courtship behavior in Drosophila is genetically hard-wired and therefore inflexible (in contrast to songbirds that learn how to sing from an adult tutor). Specifically, I will present first evidence that males can change their innate courtship ‘strategy’ after experiencing optogenetically perturbed social feedback from female flies.

Flexible circuit mechanisms for context-dependent song sequencing
Sequenced behaviors, including locomotion, reaching, and vocalization, are patterned differently in different contexts, enabling animals to adjust to their current environments. However, how contextual information shapes neural activity to flexibly alter action patterning is not yet understood. Prior work indicates such flexibility could be achieved via parallel motor circuits, with differing sensitivities to sensory context; instead we demonstrate here how a single neural pathway operates in two different regimes dependent on recent sensory history. We leverage the Drosophila song production system to investigate the neural mechanisms that support male song sequence generation in two contexts: near versus far from the female. While previous studies identified several song production neurons, how these neurons are organized to mediate song patterning was unknown. We find that male flies sing ‘simple’ trains of only one mode far from the female but complex song sequences comprising alternations between modes when near her. We characterize the male song circuit from brain to ventral nerve cord (VNC), and find that the VNC song pre-motor circuit is shaped by two key computations: mutual inhibition and rebound excitability between nodes driving the two modes of song. Weak sensory input to a direct brain-to-VNC excitatory pathway drives simple song far from the female. Strong sensory input to the same pathway enables complex song production via simultaneous recruitment of brain-mediated disinhibition of the VNC song pre-motor circuit. Thus, proximity to the female effectively unlocks motor circuit dynamics in the correct sensory context. We construct a compact circuit model to demonstrate that these few computations are sufficient to replicate natural context-dependent song dynamics. These results have broad implications for neural population-level models of context-dependent behavior and highlight that canonical circuit motifs can be combined in novel ways to enable circuit flexibility required for dynamic communication.