The experience of sleep paralysis suggests to me that there are at least two components to sleep; paralysis and suppression of consciousness and one can have one, both, or neither. With both, one is asleep in the typical fashion. With suppression of consciousness only one might have involuntary movements or in extreme cases sleepwalking. With paralysis only one has sleep paralysis which is apparently an unpleasant remembered experience. With neither, you awaken typically. The responses made by sleeping people (sleepwalkers and sleep-talkers especially) suggest to me that their consciousness is at least reduced in the sleep state. If it was only memory formation that was suppressed during sleep I would expect to witness sleep-walkers acting conscious but not remembering it, whereas they appear to instead be acting irrationally and responding at best semi-consciously to their environment.
The experience of sleep paralysis suggests to me that there are at least two components to sleep; paralysis and suppression of consciousness and one can have one, both, or neither. With both, one is asleep in the typical fashion. With suppression of consciousness only one might have involuntary movements or in extreme cases sleepwalking. With paralysis only one has sleep paralysis which is apparently an unpleasant remembered experience. With neither, you awaken typically. The responses made by sleeping people (sleepwalkers and sleep-talkers especially) suggest to me that their consciousness is at least reduced in the sleep state. If it was only memory formation that was suppressed during sleep I would expect to witness sleep-walkers acting conscious but not remembering it, whereas they appear to instead be acting irrationally and responding at best semi-consciously to their environment.