Fast near-whole-brain imaging in adult Drosophila during responses to stimuli and behavior.

Sophie Aimon,Ralph J Greenspan,Tongqiu Jia,Terrence J Sejnowski,Michael Broxton,Karl Deisseroth,Takeo Katsuki,Logan Grosenick,Josh Dubnau

doi:10.1371/journal.pbio.2006732

Abstract

Whole-brain recordings give us a global perspective of the brain in action. In this study, we describe a method using light field microscopy to record near-whole brain calcium and voltage activity at high speed in behaving adult flies. We first obtained global activity maps for various stimuli and behaviors. Notably, we found that brain activity increased on a global scale when the fly walked but not when it groomed. This global increase with walking was particularly strong in dopamine neurons. Second, we extracted maps of spatially distinct sources of activity as well as their time series using principal component analysis and independent component analysis. The characteristic shapes in the maps matched the anatomy of subneuropil regions and, in some cases, a specific neuron type. Brain structures that responded to light and odor were consistent with previous reports, confirming the new technique’s validity. We also observed previously uncharacterized behavior-related activity as well as patterns of spontaneous voltage activity.

Highlights

Measuring activity simultaneously in the whole brain is critical to understanding how different brain regions interact to process and control sensory inputs, internal states, and behavior
Whole-brain recordings give us a global perspective of the brain in action. This is already possible in humans, for which functional magnetic resonance imaging has opened a new chapter in the study of brain activity underlying behavior, but this technique has low spatial and temporal resolution
We show that the near-whole brain can be imaged with a 20x objective at a frame rate up to 200 Hz and fluorescence recorded from pan-neuronally expressed calcium (GCaMP6 [10]) or voltage (ArcLight [11]) probes

Summary

Introduction

Measuring activity simultaneously in the whole brain is critical to understanding how different brain regions interact to process and control sensory inputs, internal states, and behavior. Whole-brain recordings reveal which regions are involved in which functions and with what network dynamics and help to interpret the effects of a targeted intervention (e.g., a lesion or a local alteration with optogenetics) on the whole network and give context to local electrophysiology recordings They are necessary to characterize global changes affecting the brain on a large scale (such as different behavioral states) and detect patterns of activity involving distant regions. We apply a computational method (principal component analysis [PCA], followed by independent component analysis [ICA]) to extract components representing spatially distinct sources of activity [6,12,13] We show that these sources correspond to subneuropil areas or processes from small populations of neurons that are anatomically well characterized, and we compare their responses to flashes of light or odor puffs with those in literature reports of experiments done on restricted regions. By using this method, we discovered neuronal projections whose activity correlated with turning as well as previously unreported patterns of spontaneous voltage activity

Methods

Results

Discussion

Conclusion