Yeah, but I think "mental discretists" can tolerate that kind of very-rapid-but-still-continuous physical change - they just have to say that a mental moment corresponds to (its properties correlate with those of) a smallish patch of spacetime.

I mean, if you believe in unified "mental moments" at all then you've got to believe something like that, just because the brain occupies a macroscopic region of space, and because of the finite speed of light.

But this defense becomes manifestly absurd if we can draw out the grey area sufficiently far (e.g. over the entire lifetime of some not-quite-conscious animal.)

That, and the stability of the states on either side.