Last night, I had a truly remarkable dream. To explain what happened, I have to mention a few things:
In our dreams, we often imagine to be ourselves (or another being) doing physical actions, such as walking or talking. Of course, it would be a problem if our limbs would just move as we imagine them to do. Therefore, our brains have developed the ability to paralyze us while we sleep, i.e. to suspend our movement controls. For most people, this ability works fine most of the time. But when it doesn't, interesting things happen.
We can distinguish two scenarios:
If the paralysis is lifted while we are still sleeping, we may start to actually say things we say in our dreams, or move our arms and legs as imagined. If our consciousness starts to return just a little then, we may even sleepwalk, performing fairly complex tasks, without being truly aware of this. I think this happens to most people at some point, often more frequently as a child. Since I haven't been sleepwalking since about age 6, I can't offer a more detailed personal description.
However, sometimes our consciousness comes back while our movement control is still suspended. This is commonly called "sleep paralysis". You may then wake up and be fully aware that you are awake, lying in your bed. However, you can't move, or talk, or fully open your eyes. The first time this happens, many people are in panic (at least I was), which results in increased heart rate - but you can't even consciously control the frequency of our breath to get in more oxygen! Sometimes, there is even a feeling that an ominous force or person is approaching, or that you are being choked or suffocated. The best way to escape this situation is to calm down and fall into sleep again. Chances are good that the next time you wake up, our brain properly lifts the paralysis. This mostly happens to me when I'm trying to sleep even though I'm not really tired. My mind then sometimes enters a limbo state and drifts in and out of sleep, and occasionally ends up in a state of sleep paralysis.
While I have experienced sleep paralysis in my life, it is a fairly rare occurence - a few times a year at most. A far more common situation is a mix of the scenarios mentioned above: I am still dreaming, but try to perform actions, such as opening my eyes to examine a dream-object, which my motion control system tries to relate to actually opening my eyes - and fails. Thus, I am wandering around in my dream scenario, desperately trying to open my eyes, while an overwhelming force (the paralysis mechanism) is pushing my lids shut. As you can imagine, this is a very frustrating type of dream, and usually I eventually give up and then wake up.
This means that I'm gaining partial awareness of my sleep state - enough that I'm not satisfied anymore with my imagination of an object (or location), and instead want to actually *see* with clear vision.
Now finally about the strange experience:
Last night, incidentally after reading in Douglas Hofstadter's "Gödel, Escher, Bach", I experienced a new kind of sleep paralysis in a nested dream. I was dreaming that I was lying in my bed, sleeping and dreaming that I just awoke from a dream. However, my second-order dream-self could only move spastically with little control. I could open my eyes, but not see (only "know" my surroundings). I could get up and walk, but not speak. I fell to the ground again, crawled out of the room and moaned and mumbled incoherent things, much to the shock of my room-mate outside. I managed to explain that I was somehow partly paralyzed, and asked him to slap my face. He did, but I felt nothing. I laid down on the floor and relaxed, some movement ability returned. I got up. Back at my bed, I saw(?) that I had thrown my bedside lamp and some other things to the floor. Suddenly, a cat appeared (I have no cats), it apparently was hungry. I gave it some tuna fish and returned to bed, where I fell asleep again. That's when I awoke on the first dream layer, relieved that my paralysis was just a dream, but still annoyed that I couldn't properly open my eyes and see. I fell asleep again.
Finally, I was awake again. For a few seconds, I didn't trust reality this time, but fortunately I could actually open my eyes, and the clarity and detail of my perception quickly convinced me that I was *actually* awake. Such relief. The bedside lamp was still in place, and there was no cat.