Neurons Caught in Action: Zebrafish Brain Filmed While Firing Signals
By on March 20th, 2013

It’s the brain like never seen before. A group of researchers – Misha Ahrens, neurobiologist, and Phillipp Keller, microbiologist from Howard Hughes medical Institute’s Janelia Farm Research Campus, have been able to see individual neurons firing in the brain of a larval zebra-fish, recording activities across the entire fish brain.

And they’ve made a cool video of the whole thing (below).

They have mapped the exact firing pattern for 80% of the 100,000 neurons in the brain, suggesting that, should an upscaling of this mapping be done, the human brain might finally be in the imaging line.

The brain map - taken from the paper (link at the bottom)

The brain map – taken from the paper (link at the bottom)

The Imaging Technique

The imaging technique is ingenious, but theoretically simple. The researchers created genetically modified zebrafish, so that the neurons make a protein which fluoresces when there is a change in the concentration of the calcium ions. Calcium ion concentrations change when a neuron fires, meaning that there will be a small fluorescence when a neuron fires.

Now, a thin sheet of light was sent through the brain and this captures any optical activity in the brain and then records it on a screen. This imaging technique is called ‘light-sheet microscopy’ and the Janelia team was able to upgrade it count at a rate tenfold its original rate. The entire brain of the larval fish was mapped every 1.3 seconds. One whole experiment lasted for 10 hours, generating as much a few terabytes of data.

Ahrens commented on his pet method, explaining why it is so much better than conventional techniques. Available techniques allow one to image at most 2000 neurons at one go, but this one can see the entire circuitry in the brain. As Ahrens puts it:

you don’t need to guess what is happening — you can see it.

There is definitely room for improvement. One would be distinguish between one neuron firing and multiple firings in a short interval. Also, researchers would like to try it on other organisms.

Is the human brain up next? Not for quite some time, surely.

The work appeared here:

Author: Debjyoti Bardhan Google Profile for Debjyoti Bardhan
Is a science geek, currently pursuing some sort of a degree (called a PhD) in Physics at TIFR, Mumbai. An enthusiastic but useless amateur photographer, his most favourite activity is simply lazing around. He is interested in all things interesting and scientific.

Debjyoti Bardhan has written and can be contacted at

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