The possibility of someday recording all the neurons firing in a living creature's central nervous system has inspired generations of neuroscientists. Now a group of researchers at the Howard Hughes Medical Institute has finally achieved the feat.
The scientists studied live zebrafish larvae that had been genetically encoded with a calcium indicator called GCaMP5G. They suspended the larva in a gel and then beamed it with lasers. Just before a neuron fires, its action potential is expressed via a spike in calcium ions, so when one of the genetically modified larva's neurons reached its action potential, it glowed. This showed the researchers the firing of the neurons without them having to attach a bunch of electrodes to the fish.
Over the course of an hour the researchers used laser beams to scan the larva every 1.3 seconds, exciting the retina of the zebrafish with each scan. This microscopy method allowed ...
