This type of work started years ago. Tech is pretty simple, they hooked electrodes up to particular locations in the brain which showed significant activity in relation to particular tasks. Much like an instruction set for a CPU, depending which electrodes get a "charge" from the brain, it translates to an instruction for the CPU to execute.
This is all one-way people, there is no "hacking the brain". There is no CPU implant (or at least not yet). It is simply 8, 16, 32, etc wires coming out of your head, and you connect that to the CPU. These wires are treated (even better chance with stem-cells) so that the body/brain doesnt reject them.
I am being very general here, obviously this is serious/complex stuff, but wanted to get it out there. I for one would love to sign up and test this out.