Lisman John
Biology Department, Brandeis University, Waltham, MA, USA
Philos Trans R Soc Lond B Biol Sci. 2017 Mar 5;372(1715). doi: 10.1098/rstb.2016.0260.
Synapses are complex because they perform multiple functions, including at least six mechanistically different forms of plasticity. Here, I comment on recent developments regarding these processes. (i) Short-term potentiation (STP), a Hebbian process that requires small amounts of synaptic input, appears to make strong contributions to some forms of working memory. (ii) The rules for long-term potentiation (LTP) induction in CA3 have been clarified: induction does not depend obligatorily on backpropagating sodium spikes but, rather, on dendritic branch-specific N-methyl-d-aspartate (NMDA) spikes. (iii) Late LTP, a process that requires a dopamine signal (and is therefore neoHebbian), is mediated by trans-synaptic growth of the synapse, a growth that occurs about an hour after LTP induction. (iv) LTD processes are complex and include both homosynaptic and heterosynaptic forms. (v) Synaptic scaling produced by changes in activity levels are not primarily cell-autonomous, but rather depend on network activity. (vi) The evidence for distance-dependent scaling along the primary dendrite is firm, and a plausible structural-based mechanism is suggested.Ideas about the mechanisms of synaptic function need to take into consideration newly emerging data about synaptic structure. Recent super-resolution studies indicate that glutamatergic synapses are modular (module size 70-80 nm), as predicted by theoretical work. Modules are trans-synaptic structures and have high concentrations of postsynaptic density-95 (PSD-95) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. These modules function as quasi-independent loci of AMPA-mediated transmission and may be independently modifiable, suggesting a new understanding of quantal transmission.This article is part of the themed issue 'Integrating Hebbian and homeostatic plasticity.'
突触很复杂，因为它们执行多种功能，包括至少六种机制上不同形式的可塑性。在此，我对这些过程的最新进展进行评论。（i）短期增强（STP）是一种赫布过程，需要少量突触输入，似乎对某些形式的工作记忆有重要贡献。（ii）CA3区长期增强（LTP）诱导的规则已得到阐明：诱导并不一定依赖于反向传播的钠峰电位，而是依赖于树突分支特异性N-甲基-D-天冬氨酸（NMDA）峰电位。（iii）晚期LTP是一个需要多巴胺信号的过程（因此是新赫布式的），由突触的跨突触生长介导，这种生长在LTP诱导后约一小时发生。（iv）长时程抑制（LTD）过程很复杂，包括同突触和异突触形式。（v）由活动水平变化产生的突触缩放主要不是细胞自主的，而是依赖于网络活动。（vi）沿初级树突的距离依赖性缩放的证据确凿，并提出了一种合理的基于结构的机制。关于突触功能机制的观点需要考虑有关突触结构的新出现的数据。最近的超分辨率研究表明，谷氨酸能突触是模块化的（模块大小为70-80纳米），正如理论工作所预测的那样。模块是跨突触结构，具有高浓度的突触后致密蛋白95（PSD-95）和α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）受体。这些模块作为AMPA介导传递的准独立位点发挥作用，并且可能是独立可修饰的，这表明对量子传递有了新的理解。本文是主题为“整合赫布可塑性和稳态可塑性”的特刊的一部分。
