Markram H, Wang Y, Tsodyks M
Department of Neurobiology, The Weizmann Institute for Science, Rehovot, 76100, Israel.
Proc Natl Acad Sci U S A. 1998 Apr 28;95(9):5323-8. doi: 10.1073/pnas.95.9.5323.
The nature of information stemming from a single neuron and conveyed simultaneously to several hundred target neurons is not known. Triple and quadruple neuron recordings revealed that each synaptic connection established by neocortical pyramidal neurons is potentially unique. Specifically, synaptic connections onto the same morphological class differed in the numbers and dendritic locations of synaptic contacts, their absolute synaptic strengths, as well as their rates of synaptic depression and recovery from depression. The same axon of a pyramidal neuron innervating another pyramidal neuron and an interneuron mediated frequency-dependent depression and facilitation, respectively, during high frequency discharges of presynaptic action potentials, suggesting that the different natures of the target neurons underlie qualitative differences in synaptic properties. Facilitating-type synaptic connections established by three pyramidal neurons of the same class onto a single interneuron, were all qualitatively similar with a combination of facilitation and depression mechanisms. The time courses of facilitation and depression, however, differed for these convergent connections, suggesting that different pre-postsynaptic interactions underlie quantitative differences in synaptic properties. Mathematical analysis of the transfer functions of frequency-dependent synapses revealed supra-linear, linear, and sub-linear signaling regimes in which mixtures of presynaptic rates, integrals of rates, and derivatives of rates are transferred to targets depending on the precise values of the synaptic parameters and the history of presynaptic action potential activity. Heterogeneity of synaptic transfer functions therefore allows multiple synaptic representations of the same presynaptic action potential train and suggests that these synaptic representations are regulated in a complex manner. It is therefore proposed that differential signaling is a key mechanism in neocortical information processing, which can be regulated by selective synaptic modifications.
源自单个神经元并同时传递给数百个靶神经元的信息的性质尚不清楚。三重和四重神经元记录显示，新皮层锥体神经元建立的每个突触连接可能都是独特的。具体而言，同一形态学类别的突触连接在突触接触的数量和树突位置、它们的绝对突触强度以及它们的突触抑制率和从抑制中恢复的速率方面存在差异。在突触前动作电位高频放电期间，锥体神经元的同一轴突分别支配另一个锥体神经元和一个中间神经元，介导频率依赖性抑制和易化，这表明靶神经元的不同性质是突触特性定性差异的基础。同一类别的三个锥体神经元在单个中间神经元上建立的易化型突触连接在性质上都相似，同时存在易化和抑制机制。然而，这些汇聚连接的易化和抑制的时间进程不同，这表明不同的突触前 - 突触后相互作用是突触特性定量差异的基础。对频率依赖性突触传递函数的数学分析揭示了超线性、线性和亚线性信号传导模式，其中突触前速率、速率积分和速率导数的混合根据突触参数的精确值和突触前动作电位活动的历史传递给靶神经元。因此，突触传递函数的异质性允许同一突触前动作电位序列有多种突触表征，并表明这些突触表征以复杂的方式受到调节。因此，有人提出差异信号传导是新皮层信息处理中的关键机制，它可以通过选择性突触修饰来调节。
