Wide-field fluorescence lifetime imaging of neuron spiking and sub-threshold activity in vivo

TL;DR

This paper introduces a high-speed wide-field fluorescence lifetime imaging technique capable of capturing rapid neural activity and sub-threshold signals in vivo, advancing neuroscience imaging capabilities.

Contribution

The study demonstrates that electro-optic fluorescence lifetime imaging (EO-FLIM) achieves kHz frame rates and high temporal resolution for neural voltage imaging in live animals, overcoming previous speed and sensitivity limitations.

Findings

Achieved <5 ps lifetime resolution at 1 kHz

Successfully imaged action potentials and sub-threshold activity in Drosophila neurons

Revealed phase locking of neural spikes to external stimuli

Abstract

The development of voltage-sensitive fluorescent probes suggests fluorescence lifetime as a promising readout for electrical activity in biological systems. Existing approaches fail to achieve the speed and sensitivity required for voltage imaging in neuroscience applications. Here we demonstrate that wide-field electro-optic fluorescence lifetime imaging (EO-FLIM) allows lifetime imaging at kHz frame acquisition rates, spatially resolving action potential propagation and sub-threshold neural activity in live adult Drosophila. Lifetime resolutions of $< 5$ ps at 1 kHz were achieved for single cell voltage recordings. Lifetime readout is limited by photon shot noise and the method provides strong rejection of motion artifacts and technical noise sources. Recordings revealed local transmembrane depolarizations, two types of spikes with distinct fluorescence lifetimes, and phase locking of spikes to an external mechanical stimulus.