You ask about a universal encoder. I believe that is the central thrust of this thread.
Encode to … what?
So a universal encoder transforms whatever stream that comes to it into some common format that is readable by an SDR neuron.
The SDR is the reader of this code. What is it that an SDR reads? Conjunctions of spots of activity over a fairly short range.
If it is not intermingled grid patterns it is going to end up being something very much like it. A thought for you. If we know with a very high degree of certainty that a chunk of cortex works a certain way in one spot is it a stretch to expect it to work the same way in other places?
If it helps - the nervous system evolved to run bodies; to sense the surrounding space and relationships in that space and navigate through it. All external senses feed this basic mission. We have added some nifty tricks to this basic function but that has been the guiding principle from the start.
In the brain, we have a WHAT and WHERE stream. Each parses the raw information using different rules. The WHAT stream can parse semantic meaning by the grouping of like items. They don’t have to be physically adjacent - they only have to group in spaces that an SDR equivalent of a place cell can see them. See the cortical IO “retina” for a wonderful applied example of this idea in action.
In the WHERE stream, we already know the hippocampus reads the WHERE stream to learn places.