spectrum: The implant’s array of electrodes record electrical signals from neurons that “fire” as the person thinks of making a motion like moving their right hand—even if they’re paralyzed and can’t actually move it. By Eliza Strickland
'The BrainGate decoding software interprets the signal and converts it into a command for the computer cursor.
'Interestingly, the system worked best when the researchers customized it for each participant. To train the decoder, each person would imagine a series of different movements (like moving their whole right arm or wiggling their left thumb) while the researchers looked at the data coming from the electrodes and tried to find the most obvious and reliable signal.
'Each participant ended up imagining a different movement to control the cursor. The woman with ALS imagined moving her index finger and thumb to control the cursor’s left-right and up-down motions. [Jaimie] Henderson says that after a while, she didn’t have to think about moving the two digits independently. “When she became facile with this, she said it wasn’t anything conscious; she felt like she was controlling a joystick,” he says. The man with the spinal cord injury imagined moving his whole arm as if he were sliding a puck across a table. “Each participant settled on control modality that worked best,” Henderson says.'
"High performance communication by people with paralysis using an intracortical brain-computer interface" by Jaimie Henderson, et al, here