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. 2002 Jul 22;99(16):10831–10836. doi: 10.1073/pnas.152343099

Fig 3.

Fig 3.

Synaptic modification functions derived from model. The y axis represents normalized (final/initial) synaptic weights at the end of the induction protocol. (A) Pairing-induced plasticity. Below 62.5 mV, no change is induced; between 62.5 and 52.5 mV, LTD is induced; and above 50 mV, LTP is induced. (B) Presynaptic rate-induced synaptic plasticity, with (dashed) and without (solid) postsynaptic spikes. A similar LTP/LTD curve is obtained in both cases. The degree of similarity depends on the parameters. In the presence of postsynaptic spikes, the magnitude of LTD is decreased because postsynaptic spikes occurring at low frequency tend to fall in the LTP window. In addition, the crossover threshold between LTD and LTP is slightly lower in the presence of postsynaptic spikes. Calcium transients in the presence of postsynaptic spikes are more variable than in the absence of spikes because of the stochastic nature of spike generation. As a result, the induction of LTP and LTD is more variable (error bars on solid curve based on five runs). (C) STDP. For post-pre conditions (region I: −30 < Δt < −5 ms), LTD is induced. For pre-post conditions (region II: 0 < Δt < 45 ms), LTP is induced. Surprisingly, for larger pre-post intervals (region III: 45 < Δt < 100 ms), LTD is induced.