Fig. 2: Schematic of indexing theory.
From: Engram neurons: Encoding, consolidation, retrieval, and forgetting of memory
Schematic of indexing theory across stages. During initial learning (red stage), communication between an index region (left, akin to the hippocampus) and a perceptual region (right, akin to the neocortex) results in coordinated activity between two ensembles (triangular cells and circular cells, respectively). Consolidation (green stage) strengthens this connectivity between ensembles. Later exposure to a partial contextual cue (gold stage) incompletely activates the perceptual ensemble, but this is sufficient to drive the entire index population. This drives retrieval (teal stage), wherein complete activation of the index cells is sufficient to drive activity across the full perceptual ensemble. At each stage, arrows illustrate flow of information.
