Brains
When you speak of confabulations I am not sure that it is that simple. The day to day shared experiences are often seen as the 'real', but that in itself is a form of constructed perception. This may be where the issue of qualia arises. In many ways, colours are vibrations and it is uncertain if different species see the exact same frequencies as one another, and the whole subtle realm of vibrations.
There is also the question of inner and outer reality although it may be that it is not an absolute division because human beings dip in and out of these modes. Here, the possibility of lucid dreaming arises. This is a spectrum ranging from hypopompic and hypnagogic states as well as meditations states of awareness. It was only as a result of having some diagnosed eye problems that led me to read about the retina, which is actually part of the brain.
At one point last year I developed blurred vision in my right eye. When I had it checked out it was macular oedema, which is completely different from macular degeneration. The problem is stable, although I had to have new glasses with a stronger lens for the right eye. What is important in relation to this thread is that since I developed this problem I sometimes see intense visual images in my right eye when it is closed. This is not unpleasant and sometimes I see gardens with decorative walls and unusual symbols on walls. From what I have researched, this is connected to phosphene activity in the retina.
Oliver Sacks has written on unusual organically based experiences. Often, people expect perception to function identically. The brain is definitely involved but it still means that perception is complex, with the example of the interrelationship between sound and vision of synthasaesia.