The main achievement in optogenetics, at least so far, has been the reliable activation of neurons using light. In recent years that concept has been taken a step further with the ability to activate specific genes within those neurons using light. Researchers led by Martin Fussenegger from ETH Zürich have now implanted a living mouse with designer cells bearing genes that can be precisely controlled with light. As we will describe, that is technically challenging enough. But it is what they did next — namely, for a human wearing a brain-computer interface to remotely control the rat’s brain implant with thoughts alone — that has people talking.
The hardware pipeline they used by ETH Zurich was fairly low tech (relatively speaking, anyway). An EEG cap worn by the human picks up crude signals that reflect the general meditative state of the subject, i.e. relaxed vs less relaxed. After some signal processing, a coil almost identical to what you might find in a wireless charger is energized with a current that more-or-less varies according to that signal. The mouse, which has the implant containing the special cells which contain the special genes, sits over this coil basking in the glow of its electromagnetic field. The implant also has the receiver — basically just three orthogonal secondary coils (presumably so that some energy is intercepted regardless of the mouse’s orientation) along with a few capacitors to tune them, and a few diodes to rectify the received power so that a small DC voltage is obtained. This voltage controls a blue LED, which in turn illuminates the optogenetically enhanced cells in the implant.
That all may sound cool, but it’s something any kid with a soldering iron and enough smarts to construct a crystal radio set could handle. It’s the opto-enhanced part that would probably require a bit more support from a fairly sophisticated DIY genetics lab. The cells used are known as HEK cells, for human embryonic kidney cells. Kidney cells are generally not too exciting, although these particular fellows are now fairly omnipotent creatures by virtue of the handy genetic toolkits that have been developed for them. The cells have many of the same properties of immature neurons and can impersonate many more — not least of which being the adrenal cells that sit atop the kidney and dump grams of adrenalin into the blood during video games.
The list of all things that the researchers then did to these cells — the viral vectors, plasmids, and other elements engineered into them — takes up two pages in the supplementary methods so mercifully we won’t detail all of them here. [Research paper: doi:10.1038/ncomms6392]
Originally posted here: