Roger Penrose proposes in The Emperor's New Mind that consciousness depends not just on arrangements of synaptic connections, but on funky quantum effects. (He was on a panel discussing this at a symposium at Dartmouth while I was there studying cognitive science, and I got to ask him a question. Squee!) Collapse of the quantum waveform, decoherence, boundaries between the quantum and classical, that sort of thing. Apparently he explored that particular topic, specifically with regard to a hypothesis he has about microtubules, in his next book, (hang on, Googling/Wikiing the name...) Shadows of the Mind. I haven't read it.
Suppose he's right. Suppose consciousness relies on something like quantum computing. Well, then, decoherence would interfere with it, wouldn't it? If you could figure out a way to "observe" the essential process or feature, you could disrupt someone's consciousness.
It's too bad we have no actual clue what "observe" means. Either theoretically or practically. How do you open the box on the cat? Can we mathematically define what constitutes opening the box? Penrose touches on this; he proposes that maybe it's something like, an event is observed when it's causally connected to a one-graviton outcome. He makes it clear that he's just waving his hands, though.
What if we could causally connect consciousness to a one-graviton outcome? Something like a photomultiplier for the soul. A cascade resulting from detection of some aspect of cognition.
Like say we discover that the quantummy activity in, oh heck, let's just go with the flow and say microtubules, sometimes emits neutrinos or something. Or when consciousness is happening, it has a different probability of emitting neutrinos. I dunno, all you need is something observable. Yeah, I know what you're going to say, but just for the sake of argument let's suppose we figure out a way to detect neutrinos without a coal mine full of ultrapure water. I watch PBS sometimes, too, you know.
So there you go. Point some appropriate kind of detector at somebody's head, and disrupt their consciousness. Just like the detector in the two-slit experiment, but useful.
Wouldn't that make a rockin' weapon?