This is not a theory looking for a problem to solve, this is an attempt to explain a known process.
Note that the work in this field centers on the details at the cell level. I have been looking at this from the higher level of the nature of the engram patterns and what is special about these patterns to trigger the consolidation mechanisms described in these papers.
There are several high-level constraints that any useful theory has to explain.
- I start from the position that the index theory matchs much of the material I have read:
Max Bennett: An Attempt to Model The Neocortical Microcircuit in Sensory Neocortex - Sept 9, 2020 - #11 by dmac - I refine this with the known fact that you can recall episodes during the day before they are consolidated into the cortex. This tells me that the EC/HC index communication to the cortex is always active.
- Add to this that HM and other patients can remember episodes before the loss of the EC/HC complex so episodes can be transferred to the cortex and function there.
- The various engrams share the same computing fabric (A palimpsest) so the “readout” of the engrams must be ether sequential (seems unlikely) or a parallel process that transfers the “new” contents from all the engrams at the same time. How do they stay separated at they move from the EC/HC or map-2-map in the cortex? What is special about the newly trained columns that flags those bits to signal to the map on the other end of the fiber bundle?
- During the training period (experience of the episode) the same bundles convey experience to the EC/HC to form the index in the first place. These same bundles are bidirectional. It is entirely possible that this is the key to pushing the “new” memories back for consolidation, aligned with where they were experienced from in the first place, with the HC time cells mediating the high-level sequence part of this playback as opposed to the strict sequential replay of the original experience at the lower hierarchical levels. Do remember that the HC has a bunch of specialist cells that do object vectors, direction, distance, orientation, and time - and possibly much more that has yet to be discovered. This all had to be developed in the hierarchy (terminating in the the temporal lobe) to be presented to the the EC/HC as an experience.
Sorry in advance - this one is good but paywalled:
https://www.nature.com/articles/s41593-019-0467-3