working mechanism of braingate?

Answer 1

Detailed descriptions seem pretty hard to come by. Brown University and the Cyberkinetics corp seem to be the primary R & D source. From the ref.:
"The BrainGate Neural Interface Device is a proprietary brain-computer interface that consists of an internal neural signal sensor and external processors that convert neural signals into an output signal under the users own control. The sensor consists of a tiny chip smaller than a baby aspirin, with one hundred electrode sensors each thinner than a hair that detect brain cell electrical activity."