Goldberg Joshua A, Deister Chris A, Wilson Charles J
Department of Biology, University of Texas at San Antonio, San Antonio, TX, USA.
J Neurophysiol. 2007 Jan;97(1):208-19. doi: 10.1152/jn.00810.2006. Epub 2006 Sep 6.
The responsiveness of rhythmically firing neurons to synaptic inputs is characterized by their phase-response curve (PRC), which relates how weak somatic perturbations affect the timing of the next action potential. The shape of the somatic PRC is an important determinant of collective network dynamics. Here we study theoretically and experimentally the impact of distally located synapses and dendritic nonlinearities on the synchronization properties of rhythmically firing neurons. By combining the theories of quasi-active cables and phase-coupled oscillators we derive an approximation for the dendritic responsiveness, captured by the neuron's dendritic PRC (dPRC). This closed-form expression indicates that the dPRCs are linearly filtered versions of the somatic PRC and that the filter characteristics are determined by the passive and active properties of the dendrite. The passive properties induce leftward shifts in the dPRCs and attenuate them. Our analysis yields a single dimensionless parameter that classifies active dendritic conductances as either regenerative conductances that counter the passive properties by boosting the dPRCs or restorative conductances that high-pass filter the dPRCs. Thus dendritic properties can generate a qualitative difference between the somatic and dendritic PRCs. As a result collective dynamics can be qualitatively different depending on the location of the synapse, the neuronal firing rates, and the dendritic nonlinearities. Finally, we use dual whole cell recordings from the soma and apical dendrite of cortical pyramidal neurons to test these predictions and find that empirical dPRCs are shifted leftward, as predicted, but may also display high-pass characteristics resulting from the restorative dendritic HCN (h) current.
节律性发放神经元对突触输入的反应特性由其相位反应曲线（PRC）表征，该曲线描述了微弱的体细胞扰动如何影响下一个动作电位的时间。体细胞PRC的形状是集体网络动力学的重要决定因素。在此，我们通过理论和实验研究了远端突触和树突非线性对节律性发放神经元同步特性的影响。通过结合准有源电缆理论和相位耦合振荡器理论，我们推导出了神经元树突PRC（dPRC）所捕获的树突反应性的近似值。这个封闭形式的表达式表明，dPRC是体细胞PRC的线性滤波版本，并且滤波特性由树突的被动和主动特性决定。被动特性会使dPRC向左偏移并使其衰减。我们的分析得出了一个单一的无量纲参数，该参数将有源树突电导分类为通过增强dPRC来抵消被动特性的再生电导或对dPRC进行高通滤波的恢复性电导。因此，树突特性可以在体细胞PRC和树突PRC之间产生质的差异。结果，集体动力学可能会因突触位置、神经元发放率和树突非线性的不同而在质上有所不同。最后，我们使用来自皮层锥体神经元胞体和顶端树突的双全细胞记录来检验这些预测，发现经验性dPRC如预期的那样向左偏移，但也可能表现出由恢复性树突HCN（h）电流导致的高通特性。
