Video: Neurons sparkle as they send messages

Call them the neuron whisperers. Researchers are eavesdropping on conversations going on between brain cells in a dish.

Rather than hearing the chatter, they watch neurons that have been genetically modified so that the electrical impulses moving along their branched tendrils cause sparkles of red light (see video). Filming these cells at up to 100,000 frames a second is allowing researchers to analyse their firing in unprecedented detail.

Until recently, a neuron’s electrical activity could only be measured with tiny electrodes. As well as being technically difficult, such “patch clamping” only reveals the voltage at those specific points. The new approach makes the neuron’s entire surface fluoresce as the impulse passes by. “Now we see the whole thing sweep through,” says Adam Cohen of Harvard University. “We get much more information – like how fast and where does it start and what happens at a branch.”


The idea is a reverse form of optogenetics – where neurons are given a gene from bacteria that make a light-sensitive protein, so the cells fire when illuminated. The new approach uses genes that make the neurons do the opposite – glow when they fire. “It’s pretty cool,” says Dimitri Kullmann of University College London. “It’s amazing that you can dispense with electrodes.”

Brain in a dish

Cohen’s team is using the technique to compare cells from typical brains with those from people with disorders such as motor neuron disease or amyotrophic lateral sclerosis. Rather than taking a brain sample, they remove some of the person’s skin cells and grow them alongside chemicals that rewind the cells into an embryonic-like state. Another set of chemicals is used to turn these stem cells into neurons. “You can recreate something reminiscent of the person’s brain in the dish,” says Cohen.

Next, the team will turn their attention to epilepsy. The plan is to test drugs on a personalised “brain in a dish” to see which one is most likely to benefit someone.

And it’s not just neurons that researchers can get up close and personal with. Heart muscle cells also fire electrically as they contract. Cohen’s biotech venture, Q-State Biosciences, is taking advantage of this to look at how heart cells beat and gauge how different drugs affect their excitability.

In work presented at the Safety Pharmacology Society meeting in Washington DC this week, his team showed that several drugs that have been linked to heart problems change the firing of heart cells in a dish. “This may open up drug screening capabilities,” says one of Cohen’s collaborators, Ed Boyden of the Massachusetts Institute of Technology, who helped found optogenetics.