Ness Torbjørn V, Remme Michiel W H, Einevoll Gaute T
Department of Mathematical Sciences, Norwegian University of Life Sciences, Ås, Norway.
Institute for Theoretical Biology, Humboldt University Berlin, Berlin, Germany.
J Physiol. 2016 Jul 1;594(13):3809-25. doi: 10.1113/JP272022. Epub 2016 May 10.
The local field potential (LFP), the low-frequency part of extracellular potentials recorded in neural tissue, is often used for probing neural circuit activity. Interpreting the LFP signal is difficult, however. While the cortical LFP is thought mainly to reflect synaptic inputs onto pyramidal neurons, little is known about the role of the various subthreshold active conductances in shaping the LFP. By means of biophysical modelling we obtain a comprehensive qualitative understanding of how the LFP generated by a single pyramidal neuron depends on the type and spatial distribution of active subthreshold currents. For pyramidal neurons, the h-type channels probably play a key role and can cause a distinct resonance in the LFP power spectrum. Our results show that the LFP signal can give information about the active properties of neurons and imply that preferred frequencies in the LFP can result from those cellular properties instead of, for example, network dynamics.
The main contribution to the local field potential (LFP) is thought to stem from synaptic input to neurons and the ensuing subthreshold dendritic processing. The role of active dendritic conductances in shaping the LFP has received little attention, even though such ion channels are known to affect the subthreshold neuron dynamics. Here we used a modelling approach to investigate the effects of subthreshold dendritic conductances on the LFP. Using a biophysically detailed, experimentally constrained model of a cortical pyramidal neuron, we identified conditions under which subthreshold active conductances are a major factor in shaping the LFP. We found that, in particular, the hyperpolarization-activated inward current, Ih , can have a sizable effect and cause a resonance in the LFP power spectral density. To get a general, qualitative understanding of how any subthreshold active dendritic conductance and its cellular distribution can affect the LFP, we next performed a systematic study with a simplified model. We found that the effect on the LFP is most pronounced when (1) the synaptic drive to the cell is asymmetrically distributed (i.e. either basal or apical), (2) the active conductances are distributed non-uniformly with the highest channel densities near the synaptic input and (3) when the LFP is measured at the opposite pole of the cell relative to the synaptic input. In summary, we show that subthreshold active conductances can be strongly reflected in LFP signals, opening up the possibility that the LFP can be used to characterize the properties and cellular distributions of active conductances.
局部场电位（LFP）是在神经组织中记录的细胞外电位的低频部分，常用于探测神经回路活动。然而，解读LFP信号却很困难。虽然人们认为皮层LFP主要反映锥体细胞上的突触输入，但对于各种阈下主动电导在塑造LFP中的作用却知之甚少。通过生物物理建模，我们对单个锥体细胞产生的LFP如何依赖于阈下主动电流的类型和空间分布有了全面的定性理解。对于锥体细胞，h型通道可能起关键作用，并可在LFP功率谱中引起明显的共振。我们的结果表明，LFP信号可以提供有关神经元主动特性的信息，并暗示LFP中的偏好频率可能源于这些细胞特性，而非例如网络动力学。
人们认为对局部场电位（LFP）的主要贡献源于对神经元的突触输入以及随之而来的阈下树突处理。尽管已知此类离子通道会影响阈下神经元动力学，但主动树突电导在塑造LFP中的作用却很少受到关注。在这里，我们使用建模方法来研究阈下树突电导对LFP的影响。使用一个生物物理细节丰富、受实验约束的皮层锥体细胞模型，我们确定了阈下主动电导成为塑造LFP的主要因素的条件。我们发现，特别是超极化激活内向电流Ih可产生相当大的影响，并在LFP功率谱密度中引起共振。为了对任何阈下主动树突电导及其细胞分布如何影响LFP有一个总体的定性理解，我们接下来用一个简化模型进行了系统研究。我们发现，当（1）对细胞的突触驱动不对称分布（即要么在基部要么在顶部），（2）主动电导非均匀分布且在突触输入附近通道密度最高，以及（3）当在相对于突触输入的细胞相反极测量LFP时，对LFP的影响最为显著。总之，我们表明阈下主动电导可在LFP信号中得到强烈反映，这为LFP可用于表征主动电导的特性和细胞分布开辟了可能性。
