Crucially, the laser light and the microwaves never reach the brain tissue – not an actual human brain in this case, but tissue from the brain of a mouse – the changes in the magnetic field are simply tracked using the NV colour centres.
"When the neurons in the brain tissue sample fire, that will induce a magnetic field that then changes the light emission and the brightness of the diamond, which we record as an optical signal," says Alexander Huck.
In their experiments, the scientists can distinguish signals from different types of nerve cells. They checked their measurements using a proven technique that touched the tissue and measured the electricity directly. They also show how they can artificially change the neuron activity in the tissue by using a drug that blocks specific channels in the nerve cells.
"Eventually, the idea is that when you have a patient, where you suspect some kind of neurodegenerative disease, you may use methods derived from our experiments to diagnose the precise condition," concludes Alexander Huck. He stresses, however, that a lot of work is still needed for that to be the case:
"If we compare our technique to other methods in use today, which have been around for decades, they are still better than what we can do now. We are at an early stage, and much more work has to be done before this technique can be transferred and applied in a clinical environment. Research in NV centres and exploring their most suitable application areas is still at an early stage—this is a nascent field."