Odd ... I remember a pulp fiction short story compilation that had this exact concept in it. A soldier in a conflict against an alien race on the moon was captured and had his brain removed and installed in one of the robotic machines that humanity was fighting.

In the course of the book, he learned how to hack the network and kept causing chaos in the servitor-type androids that the aliens were using cat-brains to drive its AI.

Demons ... were, oddly enough, what they were called.

Damned if I can remember the title, though. But I think it was mid '70s fiction?

EDIT: FOUND IT!!!

https://www.goodreads.com/book/show/1829054.A_Plague_of_Demons

And it's mid '60s fiction.