Movie or TV show from 70's or 80's about a (Russian?) scientist? with brain replaced by a computer [closed]

I am going crazy searching for the movie or TV show that I saw in childhood. The plot goes like this:

A man was severely injured in some accident and lost his ability to move or talk. His brain however was perfectly healthy and well. Scientists connected his brain to a computer which learned and copied the entire function of his brain. Then they connected this computer to the nervous system of the body (which was kept alive somehow). The computer practically took control of the body, including speech and movement as a normal brain would. I clearly remember a scene where someone was talking to this guy and all seems normal, and then he flips the switch of the computer and this guys just collapses in the chair.

I also vaguely remember but unsure that this guys was some Russian nuclear scientist who was injured while studying a nuclear weapon, and he had vital information about the weapon that was needed in order to save the humanity. But I could be remembering this from something totally different. This may seem like an episode of twilight zone, but I could not find it that way.