I'm pretty sure it's just a reference to the phrase "in the loop", which dates back beyond the 80s:
Yes, "in the loop" does date back further, but as used to reference human/systems integration earliest reference I was able to find was the 80s which was the same time that Boydian like systems started popping up.
"Man in the loop" reference can be found in use by the US AirForce going back to the 80s for weapon systems design; specifically between fighter jet systems and pilots. I've heard that US AirForce used brain implants as early as the 90s in fighter pilots.
Here's an example of the US Army reads soldier's brain waves to speed up image analysis:
http://newatlas.com/us-army-eeg-brainwave-image-analysis/403...