(Image: Looger Lab, HHMI/Janelia)

These images capture a chunk of a mouse brain lighting up at a moment in time as the animal watches an animation. The gif, which moves through slices of the 3D image, was captured using a new protein sensor that changes colour from green to pink to reflect brain activity.

Developed by Benjamin Fosque from the University of Chicago and his colleagues, the fluorescent protein sensor, called CaMPARI, gives off light in response to the change in calcium concentration in neurons, which is linked to activity. To activate the fluorescence, just shine a violet light on the protein.

(Image: Looger Lab, HHMI/Janelia)


Although the mouse was immobilised during brain imaging, this zebrafish larva was imaged while swimming around in calm water. The researchers also took pictures of its brain in hot, cold and turbulent water to compare the brain activity in these circumstances.

Existing brain imaging methods use similar calcium indicators, but can’t show such large volumes of tissue. Since the colour changes they cause are short-lived, a microscope must be carefully focused in advance to capture a moment, so only a small area of cells can be photographed.

The new sensor causes a long-lasting colour change. A 3D “tattoo” of the activity is created while the animal is freely moving around, giving researchers time to zoom in on different areas under a microscope afterwards. “At the moment they are performing the behaviour you are interested in, you can flash a pulse of light labelling the neurons involved,” says Fosque.

Allowing animals to move freely during imaging should be useful when studying complex behaviour like social interactions and courtship. “It would be cool to see patterns of activity when an animal meets a new member of its species for the first time,” says team member Eric Schreiter from the Howard Hughes Medical Institute in Ashburn, Virginia.

Journal reference: Science, DOI: 10.1126/science.1260922