I read that this is a Dollhouse reference, but sadly I didn't watch that show...
The basic idea in Dollhouse was that they could turn the dolls on and off while manipulating their personalities. So an exchange where the doll interpreted being turned off as falling asleep was common. The primary suggestion here would be that Coulson was not experiencing what he thought he was experiencing.
If you don't mind spoilers from well after the eighth episode, we eventually find out that
T.A.H.I.T.I. was a project that Coulson ran at S.H.I.E.L.D. So they not only made him forget what happened to him but also what he had already known. As part of what they were doing, they removed the top of his skull, leaving the brain exposed. They would directly stimulate the brain with needles (and possibly electric current, although I'm not sure that was stated). They would also apply Kree fluid for its regenerative properties. The memory erasure procedure was supposed to compensate for the side effects.
But as I said, this was explained well after the eighth episode, mostly in bits and pieces. If you don't mind spoilers, you can read more about it at Project T.A.H.I.T.I..