I'm impressed they get that much accuracy from the motor cortex. I posted this[1] before - I imagine detecting signals at the spinal cord would provide even greater accuracy (not necessarily in this case). I'm really excited either way.

I'd like to know more about the implanted array though. My impression was that all arrays induce scarring and lose effectiveness over time.

Also, isn't paralysis in ALS caused by the death of motor neurons? If that's so, what exactly was the array sampling? Is it just that there's too few neurons to control muscles, but still enough to type?

[1] http://journal.frontiersin.org/article/10.3389/fnins.2014.00...