Existing electrophysiological and fluorescence-based brain imaging techniques in mice are generally invasive, require head fixes or cables, and are not suitable for long-term recordings. While there have been recent advances in imaging methods in freely moving animals, these are major limitations for researchers that are interested in the brain correlates of social behaviors.

The color of LOTUS-V bioluminescence changed from cyan to green when neurons in a brain were activated. (Credit: Osaka University)

Researchers have developed a new method to record brain activity simultaneously in multiple, freely moving mice. The method is based on a recent bioluminescence-based indicator of membrane voltage called “LOTUS-V.” The LOTUS-V bioluminescent probe is genetically encoded, which means that it is delivered to target cells noninvasively via a common gene expression system (the adeno-associated virus). Its signal is derived from cell membrane voltage changes, which reflect brain activity.

The LOTUS-V method reported brain activity in freely moving mice with a good sensitivity and without motion artifacts. More importantly, it could measure dynamically changing brain activity in the primary visual cortex during social interactions.

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