van Rossum M C, Bi G Q, Turrigiano G G
Brandeis University, Department of Biology, Waltham, Massachusetts 02454-9110, USA.
J Neurosci. 2000 Dec 1;20(23):8812-21. doi: 10.1523/JNEUROSCI.20-23-08812.2000.
We explore a synaptic plasticity model that incorporates recent findings that potentiation and depression can be induced by precisely timed pairs of synaptic events and postsynaptic spikes. In addition we include the observation that strong synapses undergo relatively less potentiation than weak synapses, whereas depression is independent of synaptic strength. After random stimulation, the synaptic weights reach an equilibrium distribution which is stable, unimodal, and has positive skew. This weight distribution compares favorably to the distributions of quantal amplitudes and of receptor number observed experimentally in central neurons and contrasts to the distribution found in plasticity models without size-dependent potentiation. Also in contrast to those models, which show strong competition between the synapses, stable plasticity is achieved with little competition. Instead, competition can be introduced by including a separate mechanism that scales synaptic strengths multiplicatively as a function of postsynaptic activity. In this model, synaptic weights change in proportion to how correlated they are with other inputs onto the same postsynaptic neuron. These results indicate that stable correlation-based plasticity can be achieved without introducing competition, suggesting that plasticity and competition need not coexist in all circuits or at all developmental stages.
我们探索了一种突触可塑性模型，该模型纳入了近期的研究发现，即通过精确计时的突触事件对和突触后尖峰可诱导增强和抑制。此外，我们还纳入了这样的观察结果：强突触比弱突触经历的增强相对较少，而抑制与突触强度无关。随机刺激后，突触权重达到一个稳定、单峰且具有正偏态的平衡分布。这种权重分布与在中枢神经元中实验观察到的量子幅度分布和受体数量分布相比具有优势，并且与在没有大小依赖性增强的可塑性模型中发现的分布形成对比。同样与那些显示突触之间存在强烈竞争的模型不同，该模型在几乎没有竞争的情况下实现了稳定的可塑性。相反，可以通过纳入一种单独的机制来引入竞争，该机制根据突触后活动以乘法方式缩放突触强度。在这个模型中，突触权重的变化与它们与同一突触后神经元上的其他输入的相关性成比例。这些结果表明，无需引入竞争即可实现基于相关性的稳定可塑性，这表明可塑性和竞争不一定在所有回路或所有发育阶段共存。
