[@Necroes] I'd expect that most are actually connected to the Marine's [i]nerves,[/i] which in turn link up to certain portions of their brain. Plenty probably have a brain connection, if their effects are more passive than anything else, but I wouldn't expect most to need outright brain surgery even if seriously mangled. Just because you lose an arm, doesn't mean you can't control an artificial one by any means other than directly altering your brain structure to sync up with it.