Characterization of Proprioceptive System Dynamics in Behaving Drosophila Larvae Using High-Speed Volumetric Microscopy

Rebecca D Vaadia,Wenze Li,Venkatakaushik Voleti,Aditi Singhania,Elizabeth M.C Hillman,Wesley B Grueber

doi:10.1016/j.cub.2019.01.060

Rebecca D Vaadia, Wenze Li + Show 4 more

Open Access

https://doi.org/10.1016/j.cub.2019.01.060

Copy DOI

Abstract

SUMMARYProprioceptors provide feedback about body position that is essential for coordinated movement. Proprioceptive sensing of the position of rigid joints has been described in detail in several systems; however, it is not known how animals with a flexible skeleton encode their body positions. Understanding how diverse larval body positions are dynamically encoded requires knowledge of proprioceptor activity patterns in vivo during natural movement. Here we used high-speed volumetric swept confocally aligned planar excitation (SCAPE) microscopy in crawling Drosophila larvae to simultaneously track the position, deformation, and intracellular calcium activity of their multidendritic proprioceptors. Most proprioceptive neurons were found to activate during segment contraction, although one subtype was activated by extension. During cycles of segment contraction and extension, different proprioceptor types exhibited sequential activity, providing a continuum of position encoding during all phases of crawling. This sequential activity was related to the dynamics of each neuron’s terminal processes, and could endow each proprioceptor with a specific role in monitoring different aspects of body-wall deformation. We demonstrate this deformation encoding both during progression of contraction waves during locomotion as well as during less stereotyped, asymmetric exploration behavior. Our results provide powerful new insights into the body-wide neuronal dynamics of the proprioceptive system in crawling Drosophila, and demonstrate the utility of our SCAPE microscopy approach for characterization of neural encoding throughout the nervous system of a freely behaving animal.

Highlights

Monitoring neural activity in freely behaving animals is a key step toward understanding how sensory activity is transformed into action [1,2,3]
Multispectral, high-speed, volumetric swept confocally aligned planar excitation (SCAPE) microscopy is capable of characterizing tissue and cellular dynamics in live behaving animals [9, 10]
Identi- To begin to characterize proprioceptor dynamics as larvae fying the specific roles of each cell type is not possible without crawl, we focused on the ventral posterior dendritic arborization measuring the system’s dynamic activity patterns during natural class I neuron (Figure 1A)

Summary

Introduction

Monitoring neural activity in freely behaving animals is a key step toward understanding how sensory activity is transformed into action [1,2,3]. Light-sheet, confocal, and two-photon microscopy can capture neuronal calcium activity in isolated Drosophila brains or immobilized preparations [4,5,6,7,8]. These methods have been unable to provide volumetric imaging at sufficient speeds, in unrestrained samples, to enable extended imaging of body-wide neural activity in behaving animals. Multispectral, high-speed, volumetric swept confocally aligned planar excitation (SCAPE) microscopy is capable of characterizing tissue and cellular dynamics in live behaving animals [9, 10] We have applied this imaging technology to characterize the dynamics of multidendritic (md) neuron activity in crawling Drosophila larvae.

Methods

Findings

Discussion

Conclusion