标题： 神经元作为奖励调节的组合开关和学习行为的模型 显示英文标题

标题： Neuron as a reward-modulated combinatorial switch and a model of learning behavior

摘要： 本文提出了一种神经元电路布局和突触可塑性原则，使得（锥体）神经元能够充当“组合开关”。 也就是说，当那些先前的神经元放电之后跟随有正向全局奖励信号的输入神经元放电组合时，神经元会学习更倾向于产生尖峰。 奖励信号可能由某些调节性激素或神经递质介导，例如多巴胺。 更一般地说，建议了一种试错学习范式，在这种范式中，全局奖励信号会触发神经元对先前神经元输入放电模式的尖峰反应的长期增强或削弱。 因此，奖励提供了一条反馈路径，告知神经元其尖峰对于特定输入组合是有益还是有害的。 神经元辨别特定输入神经元放电组合的能力是通过输入突触在树突上的随机或预定的空间分布实现的，这种分布创造了代表各种输入神经元排列的突触簇。 相应的树突段，或所包含的单个树突棘，由于涉及电压门控通道传导的局部S型阈值处理，如果该段的兴奋性输入和抑制性输入的缺失在时间上是重合的，那么它们能够被特别兴奋。 这种非线性兴奋对应于输入神经元的特定放电组合，并且认为兴奋强度编码了组合记忆，并由长期可塑性机制进行调节。 还建议，可能由时空突触输入重合引起的树突棘钙离子内流可能导致树突棘头部的肌动蛋白丝发生机械（类似肌肉）收缩，随后的细胞骨架变形会传递到轴突初始段，可能会…… 显示英文摘要

摘要： This paper proposes a neuronal circuitry layout and synaptic plasticity principles that allow the (pyramidal) neuron to act as a "combinatorial switch". Namely, the neuron learns to be more prone to generate spikes given those combinations of firing input neurons for which a previous spiking of the neuron had been followed by a positive global reward signal. The reward signal may be mediated by certain modulatory hormones or neurotransmitters, e.g., the dopamine. More generally, a trial-and-error learning paradigm is suggested in which a global reward signal triggers long-term enhancement or weakening of a neuron's spiking response to the preceding neuronal input firing pattern. Thus, rewards provide a feedback pathway that informs neurons whether their spiking was beneficial or detrimental for a particular input combination. The neuron's ability to discern specific combinations of firing input neurons is achieved through a random or predetermined spatial distribution of input synapses on dendrites that creates synaptic clusters that represent various permutations of input neurons. The corresponding dendritic segments, or the enclosed individual spines, are capable of being particularly excited, due to local sigmoidal thresholding involving voltage-gated channel conductances, if the segment's excitatory and absence of inhibitory inputs are temporally coincident. Such nonlinear excitation corresponds to a particular firing combination of input neurons, and it is posited that the excitation strength encodes the combinatorial memory and is regulated by long-term plasticity mechanisms. It is also suggested that the spine calcium influx that may result from the spatiotemporal synaptic input coincidence may cause the spine head actin filaments to undergo mechanical (muscle-like) contraction, with the ensuing cytoskeletal deformation transmitted to the axon initial segment where it may...