Hebbian plasticity in parallel synaptic pathways: A circuit mechanism for systems memory consolidation
Fig 4
Consolidation of place-object associations in multiple hippocampal stages.
(A) Structure of the extended model. PPSUB: perforant path to the subiculum. Each area (EC, DG-CA3, CA1, SUB) contains object-coding and place-coding populations. Open arrows: all-to-all connections between these areas. (B) Decoding of consolidated associations. Top: The location of a platform in a circular environment is stored as an object-place association in the SC (thick diagonal arrows in A, right). Middle: Platform position probability maps given the platform object cue, inferred from the CA1 output resulting from SC or PPCA1 alone, at different times during consolidation (see section “Consolidation of place-object associations in multiple hippocampal stages” in Methods). Bottom: Platform-in-quadrant probabilities (±SEM) given PPCA1 input alone during consolidation. Quadrant with correct platform position (target quadrant) in orange. (C) Consolidation from SC to PPCA1 and to PPSUB over four weeks. Each day, a new association is first stored in SC and then partially consolidated. An association on day 0 is monitored in SC, PPCA1, and PPSUB. Panels as in B. (D) Effects of PPCA1 lesions on memory consolidation, model and experiment (data with permission from [27]). Histograms of time (±SEM) spent in quadrants at different delays after memory acquisition (“probe”). Dashed lines at 25% are chance levels. T: target quadrant; Left, Right: adjacent quadrants; O: opposite quadrant. Top: Control without lesion. Middle: Lesion before memory acquisition. Bottom: Lesion 21 days after memory acquisition.