[Martin Taylor 2017.12.05.13.08]
[From
Rupert Young (2017.12.05 17.00)]
(Martin Taylor 2017.12.05.11.45]
Is this just PCT by another name? And
they are using “prediction” in place of “reference”?
If you keep all CSGnet messages, as I do, you might re-read
[Martin Taylor 2017.09.15.17.52] reposted 2017.09.19.17.27.
which treats the similarities and differences between the
Predictive Coding Theory (PreCoT) and the Perceptual Control
Theory (PerCoT) circuitry for a control loop including the
imagination connection and the connections between levels. If
not, I imagine it is in Dag’s archives, or I could send a copy.
I can see one "reposted 2017.09.19.17.25" entitled "What is
revolutionary about PCT?", is that it?
No. The subject line is Re: Slatestarcodex, and the repost date ends
“.27”. I guess you don’t have it, so here’s the relevant part of the
text of it. “PreCoT” = Predictive Coding Theory. “PerCoT” =
Perceptual Coding Theory".
================quote===========
A few weeks ago I offered an alternative circuit for the inter-level
connections in PerCoT. I don’t remember whether I said so at the
time, but it was based on one by Seth and Friston to demonstrate
PreCoT. It isn’t exactly the same as their diagram, but it is my
interpretation of their diagram in PerCoT visual language. I used
this figure to show that different physical (neural) connections can
provide the same result. In it, the error is routed both up and down
(through the output function that provides the next lower layer’s
reference values.
In the "standard" PerCoT connection (top row), what goes up to the
next level is the perceptual value. In the PreCoT-based circuit what
goes up is the error and the reference, from which the Perceptual
Function can produce the perceptual signal (if that loop requires
it). The left column shows this for the “standard” no-tolerance,
no-imagination condition. The middle column shows how the two
circuits treat tolerance, while the right column shows how they both
treat imagination.
The PreCoT-based circuit can do whatever the standard PerCoT circuit
can do, but it can do other things as well, such as inject either
reference or error individually back into the upgoing perceptual
circuitry. The PreCoT circuit also automatically allows for blending
of appropriately weighted sensory and imagination input, as Bruce
(Nevin?) was arguing for, many months ago. I consider both to be
advantages, because we certainly can (at least consciously) perceive
reference and error separately from the current perception, and the
current perception does use partial input from imagination if the
sensory input isn’t very clear or is interrupted…
I'm not guaranteeing that my interpretation of PreCoT would be
accepted as correct by one immersed in that theory, but I don’t
think it can be too terribly wrong. I haven’t really studied PreCot
beyond reading a few articles. If it is anything like correct, the
important difference between PreCoT and PerCoT isn’t in what the
circuitry does functionally, so much as in the labels attached to
the components by the proponents of the two theories.
There is one very big difference not captured in the above diagram,
however, and that is in the internal nature of the output functions,
which in PreCoT need to perform complex computations in real time to
work out what actions to perform to minimize what they call
“prediction error”, whereas PerCoT requires the output function
mainly to provide Gain, and if the environmental feedback path does
not provide it, time-binding in the form of integration. In PerCoT,
the equivalent of the complicated calculations is largely contained
in the reorganized structure of the hierarchy, which determines what
actions tend to work best in influencing a controlled perception.
=======end quote=======
Martin