Yes,my reply to that post, together with your diagram, is at An alternative hierarchic connection circuit (was Re: Perceptual Cartoon).
In brief, I liked this way of having imagination always ‘on’, constituting the perceptual signal in the absence of perceptual input from below, and having negligible influence on the perceptual signal when there is perceptual input from below. More sophisticated than the way of doing it that I suggested in my chapter of the Handbook. I thought it might take a while to suss out unforeseen complications.
But the question at hand is not how the imagination signal is generated, but rather, can you perceive an error signal. In the Friston/Taylor proposal the imagined perceptual input results from synapsing error and reference together. The error signal never by itself constitutes a perceptual signal. (And error is zero when the perception is entirely imaginary, with no perceptual input from below, right?)
The ‘classical’ view is, no, you can’t perceive an error signal and you can’t be aware of an error signal; that is still my view. So you asked
This actually echoes questions that I asked and which you quoted in that 2017 thread that you referenced.
Yes, I can direct my attention to an imagined perception of the desired state of affairs from the point of view of the comparator which sets that reference signal. In a tracking example, that comparator is above the relationship level, setting a reference for ‘cursor at target’ as means of controlling its purpose, ‘satisfy the experimenter,’ perhaps. And I can direct my attention to the actual spatial relationship between cursor and target. To do that, my attention is from the point of view of the relationship comparator. Can I attend to both perceptions at once? Perhaps, but more likely my attention shifts between them.
The disparity between the imagined perception (the reference value for the relationship) and the ‘actual’ perception could conceivably be perceived as some kind of relationship perception, but that is not the error signal.
It may be confusing sometimes that we do perceive the somatic consequences of error. I believe this ‘affect effect’ is extremely important for clinical applications, and have suggested that to Eva.
Over the years I have occasionally heard phrases like ‘experiencing error’ and it has seemed to me that these phrases express this confusion. At the heart of it is the very important and puzzling distinction between perception-as-experienced and perceptual signal.
The experience of perceiving is all we directly have. Indirectly, inferentially, we have theories and models. ‘Perceptual signal’ is an experienced perception for a neuroscientist under certain experimental conditions, but for the most part, ‘perceptual signal’ is a theoretical entity in a model, and though the relationship between the former and the latter has been demonstrated in certain experiments it is more often assumed. We have a good grasp of each end of the relationship between ‘perceptual signal’ and ‘perception-as-experienced’, but the presumed bridge between them is quite foggy. The reason it is foggy is that intellectual constructs and immediate experience seem to be incommensurate in character. The point of science is to use the former to explicate the latter, and use the latter to test and refine the former.
The error signal is firmly on the theoretical construct side, with some few glimpses perhaps by neuroscientists, and our awareness of feelings and emotions is firmly on the experiential side. Feelings are perceptions in the somatic branch of the hierarchy and emotions are perceptions interpreting those feelings at levels above the divergence of the behavioral and somatic branches.
I refer to Bill's PCT model of emotion (version 2).
I elaborated a bit on An opinion of the brain about sensations in the body.