Nature Neurosci. doi:10.1038/nn.2518 (2010)

Monitoring the activity of specific brain cells in vivo using fluorescence imaging typically requires animals to be restrained or anaesthetized. A new method that exploits bioluminescence overcomes this limitation — at least in small creatures.

Florian Engert of Harvard University in Cambridge, Massachusetts, and his colleagues created transgenic zebrafish larvae in which selected sets of brain neurons expressed the jellyfish bioluminescent protein aequorin fused with green fluorescent protein, which together respond to changes in neuronal calcium-ion levels. A large-area photodetector above the fishes' tank reported their neuronal activity as they swam freely over several days. Achieving high temporal resolution but limited spatial resolution, the authors identified different classes of neural activities associated with different swimming behaviours.

The method is applicable to animals small enough to move freely within the range of a detector, such as fruitflies and nematode worms, the authors say.