In the category of informed speculation based on practice experiences:
There appears to be no sensation in the unconscious mind itself. Literally, doctors can do surgery in the brain without anesthesia because the interior of the brain does not feel sensations. If they touch a neural bundle it can trigger a memory.
Without sensation, there can be no creation of the experience of time in the unconscious mind itself. A stasis chamber in science fiction holds human beings but stops time. It appears that the unconscious acts like a stasis chamber for human memories and perhaps thought streams too
An interesting meditation is to focus attention on the center of the brain where there is no sensation. How? By body scanning for sensations, then withdrawing inwards, focusing inwards, to the ‘space without sensations.’
A corollary is that individual word or image thoughts arising in the space of conscious awareness have no sensations at all–all the sensation connected to the individual thought or image appear to be arising elsewhere in the body, not in the mental space where the conscious mind notices them.
When the attention is completely focused inward on the space without sensations, there is a disconnect from regular bodily and selfing awareness. This could be the physical basis for the experiences reported by many of ‘primordial awareness.’ The stasis chamber of the unconscious mind is physical and therefore the effects produced within it are not permanent, even if they appear to be that way.