I have interesting experience long time ago. In the near-sleep state my consciousness split in two streams - one was some hypnogogic images, and the other was some hypnogogic music.
They was not related to each other and each had, some how, its own observer.
A moment later something awakened me a bit and the streams seamlessly merged and I was able to observe that a moment before I had two independent streams of consciousness.
Conclusions:
1. A human can have more than one consciousness at the time.
2. It actually happens all the time but we don't care.
3. Merging of consiosnesses is easy. Moreover, binding and merging is actually the same process similar to summation.
There is no center of consciousness - homunculus or electron or whatever.
I may have other conscious processes in the brain which just do not merge with current stream of consciousness.
Qualia remain the same and preserve in each of the streams of consciousness.
I was not dreaming. I was observing my hypnagogic images, which is not the same as dreaming; and when streams merged I become completely awake.
However, after I know what is it, I can observe similar thing again. The receipt is following:
1. do two different unrelated things which require conscious attention but happen in different modalities, audio and video
2. increase the wideness of attention and observe that you just had two streams of more narrow attention.
The closest thing in everyday life is "driver amnesia" - the situation when a car driver is splitting attention between driving and conversation.