This is very cool and technically challenging. I cannot imagine how hard it was to get viral transfection in the ear like that! Seriously, props. In almost all

This is very cool and technically challenging. I cannot imagine how hard it was to get viral transfection in the ear like that! Seriously, props. In almost all applications, optical stimulation theoretically (and in rodent trials) outperforms electrical stimulation. Once we solve the immunological roadblocks of optogenetics, I can imagine a huge spike in peripheral nervous system applications. Perhaps not as much in the CNS, since deep brain stimulation is a huge problem. That being said, the immunological problem in optogenetics is the elephant in the room. I think everyone in the field knows that long-term loss-of-expression is heavily influenced by immune responses, yet are afraid to admit it. Essentially, if transfecting adults with light-gated ion channels leads to horrific immunological feedback, we could see people getting worse as their nerves are destroyed. I have seen this in my histological samples (PNS; hindlimb; rats and mice) and have quantified denervation atrophy by post-mortem weighing of muscle. This is not a solved problem, even though a few promising solutions like drug treatments and chimeric protein engineering are being discussed. I suspect certain immunosuppressant drugs might be particularly effective. Despite the risks above, start-ups are trying to take this very promising technology to human trials. I personally find this reckless. But I'm done with the negativity: the study in the OP is really awesome and I'm rooting for them. I dream of a day when opto is advanced enough that targeted, multi-color activation of sensory neurons is translated to people. Imagine feeling force and touch with a prosthetic because it talks directly to your nervous system... maybe one day :)