Brain Activity In Freely Moving Mice

Brain functions and related psychiatric disorders have been investigated by recording electrophysiological field potentials. Electroencephalography (EEG) measures whole brain wide activity; while local field potential recording detects the dynamics of more localized micro-networks of the neurons.

Electrophysiological  field potential dynamics have been widely using to investigate brain functions and related psychiatric disorders. Considering recent demand for its applicability to freely moving subjects; especially for animals in a group and socially interacting with each other; here we propose a new method based on a bioluminescent voltage indicator LOTUS-V.

Taking advantage of our method as a fiber-free system, we further succeeded in simultaneously recording from multiple independently-locomotive mice that were freely interacting with one another; Importantly, this enabled us to find that the primary visual cortex, a center of visual processing, was activated during the interaction of mice.

Voltage Imaging In Neurons Using LOTUS-V

Using our fiber-free recording method based on the LOTUS-V; we succeeded in capturing dynamic change of brain activity in freely moving mice. Because LOTUS-V is the ratiometric indicator, motion and head-angle artifacts were not significantly detected.

Taking advantage of our method as a fiber-free system; we further succeeded in simultaneously recording from multiple independently-locomotive mice that were freely interacting with one another.LOTUS-V consists of a voltage-sensing domain from voltage-sensing phosphatase; NLuc, and Venus An increase of the membrane voltage causes a structural change of the VSD; enhancing Forster resonance energy transfer between the NLuc and Venus; which consequently decreases the NLuc signal and increases the Venus signal and thus allows the ratiometric measurement.

LOTUS-V Report Brain Activity

This study previously demonstrated that the ratiometric measurement by LOTUS-V is useful to monitor voltage changes in HEK293T cultured single cells and moving cardiomyocyte aggregates. We verified the advantages of LOTUS-V in long-term imaging and the robustness of the signal reliability in a moving specimen.

We first tested the efficacy of LOTUS-V for in vivo imaging of brain activity from an awake mouse; using a head-fixed system. LOTUS-V is locally expressing in the primary visual cortex (V1) using the adeno-associated virus (AAV) gene expression system; and labelled a population of local neurons in the V1

Present study demonstrated that imaging with the LOTUS-V is a powerful and motion-artifact-free method to monitor neural activity from a target brain area of freely moving multiple mice.Overall; our method opens a door to an easy and minimally invasive recording of brain activity simultaneously in multiple socially interactive animals; thus, contributing to a wide range of neuroscience research.