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

Figure 2

Simulated distributions of synaptic weights. (a) Distribution for 1,000 independent clusters with . Black trace, histogram with 80 bins illustrating an approximately log-normal distribution of the 10,000 weights. Each bin is equal in width in natural log units. Red curve, a log-normal distribution (mean at 0.0131, standard deviation of 0.9341), fitted by MATLAB, that approximately reproduces the histogram. The histogram was constructed after 50,000 simulated days to ensure a steady state. (b) Black and red traces, similar to (a), except the mean and standard deviation of LTP, parameters and , are fixed at 0.16 and 0.04, respectively. Blue trace, the histogram of is shifted to much lower values when is decreased by 2%. (c) Weight dynamics without regeneration of synapses. The histogram of the active synapses shifts to much greater values (black trace). ~45% of synapses are silent, unable to regenerate, and not included in the histogram. This histogram is an approximate steady state, although with no regeneration, all synapses would become silent after a much longer time. Red curve, normal distribution from (a).

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