Modeling Maintenance of Long-Term Potentiation in Clustered Synapses: Long-Term Memory without Bistability

Figure 1

Schematic illustrating key model elements. Two silent synapses, corresponding to two small dendritic spines, are adjacent to two active synapses corresponding to larger spines. Only the silent synapse next to an active synapse is currently eligible for regeneration. Although the dynamics of mRNAs or locally synthesized proteins are not simulated, large synapses are implicitly assumed to capture more of these resources. This is illustrated by a greater flow of mRNAs (colored strands) onto ribosomes near the largest synapse and a greater flow of plasticity-related proteins (PRPs) into that synapse. This resource capture attenuates the amount of resource available to support growth of all synapses in the cluster. The average amplitude of LTP events is thereby reduced when more synapses in a given cluster are strong.