Are quadruplegics the same people, even if their body-image is going to the dogs? Are people with anaesthesized spinal cord still people or not? That's an experiment which is easy enough to try.
A hard validation would be a whole-head graft, which has been successfully done with animals. They attempted to vocalize/bite the experimenter (which is not very surprising -- I think in their place I'd try that, too). For some strange reason (duh), this has not been tried with people yet.
There are certainly individually distinct low-level motorics present in the spinal cord -- however, these can be learned or even convincing surrogates be installed in their place -- after all, ressurection does require nontrivial level of technology.
Lee Daniel Crocker writes:
> > If the heart consists of 60-65% brain, what are the implications
> > for head-only cryonic suspension?
>
> Head-only cryonic suspension has always been dubious (beyond the
> level that cryonics itself is) even without this. This particular
> "thinking with the heart" story is almost certainly a meaningless
> extrapolation from a small discovery motivated by mysticism, but
> that doesn't mean all such notions are nonsense.