Just read an interesting paper (don't be fooled by the cryptic title) reporting a study led by neuroscientists at the University of Chicago on where one should stimulate the brain cortex to create the sensation of touch.
Why would you want to do that? Well, if you lost a limb there are now sophisticated prosthetics that can replace it and there are ever more perfected ways to communicate to the limb and the hand what you want them to do. Electrical signals from the brain reach the connection points of the prosthetics (or muscular movements induced by those signals on the stump) and direct its operation.
A big issue is the feedback. Whatever we are doing is the result of very fine interaction between an action and its result. When you pick up a egg or a glass of wine the approach is the same but the strength you apply to the egg shell or to the glass stem are quite different and you know exactly what is the right amount of pressure by the feedback your brain receives from the sense of touch, from your fingers.
This is where the study carried out at the University of Chicago (and in other research labs connected to it) matters. It is no longer a problem to have sensors embedded in prosthetic fingers and joints so we can have an electrical signal that is proportional to the pressure applied (which in turns depends on the object we are touching) but the problem is how to exploit these signals by the brain.
The researchers have found the right spots on the brain cortex and the right way to activate them to re-create the natural sensation of touch and that will provide the brain with the needed feedback.
This is a first step going beyond application in prosthetics. It is a step in the direction of a human to robot symbioses where there is a seamless interchange of information between our brain and the robot "brain".
Clearly, the idea of sticking wires into my brain is not on top of my wish list, but there are studies to get rid of electrodes substituting them with magnetic fields that can be generated outside of the skull. These magnetic fields in principle can be pinpointed to specific neural circuits by sensitising them, in a way similar to the approach used in optogenetics. The way is still very long, and winding, but it looks like there may be a way....