Light-sheet microscope records voltage from about a quarter of a larval zebrafish's brain neurons

What happened

Whole-brain imaging of neural activity has mostly relied on calcium indicators. Imaging voltage directly across a brain demands a microscope with both a very high volumetric rate and a good signal-to-noise ratio.

The researchers built a remote-scanning light-sheet microscope that images neurons expressing a genetically encoded voltage indicator throughout much of the larval zebrafish brain at 200.8 volumes per second. They measured voltage traces from approximately one quarter of all neurons in the brain. Neurons that fired at different times in a sequence sat in different places: sequences evoked by visual stimuli mapped across the optic tectum, while bursts that occurred independently of stimuli mapped across the cerebellum and medulla.

Why it matters

Neurons interact in networks spread throughout the brain. Recording voltage, not calcium, from a large fraction of a vertebrate brain at once opens the way to studying how electrical activity is coordinated across regions.

Caveats

This entry is based on the abstract. The method covers much of the brain and about a quarter of its neurons, not all of them, and it depends on the small, transparent brain of the larval zebrafish. The abstract does not state whether single action potentials were resolved.