I have a theory that your personal space is the regions you can interact with directly using your body.
The mapping of your body in this space will include what it looks like with your hands and feet placed in this space.
This interpersonal space is special because it is the direct extension of your sense of self and agency.
Put in a different way - you learn all the ways your joints and support/vestibular system can be combined and at the same time your vision learns what it is like to see you in these places. This body mapping includes your head and eye positions relative to both your body and the supporting surface. This mapping is the fused location signal that is built up in the parietal lobes.
This constructed location signal is what is often referred to indirectly in much of the Numenta literature.
I should add that the mapping from ego-centric space starts here. The world around you is at “the other end” of your vestibular system and support/balance system - the reference frame that you use to anchor your interpersonal space. This mapping of your body is the transformation matrix back to the rest of the world.
If you find this general topic interesting I have some more references on the sense of self, agency, and personal space here and here.