Laboratory of Computational Neuroscience, Unité de Neurosciences, Information et Complexité, CNRS, Paris 91190 Gif sur Yvette, France.
Institut National de la Santé et de la Recherche Médicale, CNRS, Institut De La Vision, Sorbonne Universités, Paris F-75012, France.
eNeuro. 2018 Jun 5;5(3). doi: 10.1523/ENEURO.0068-18.2018. eCollection 2018 May-Jun.
Action potentials (APs) are electric phenomena that are recorded both intracellularly and extracellularly. APs are usually initiated in the short segment of the axon called the axon initial segment (AIS). It was recently proposed that at the onset of an AP the soma and the AIS form a dipole. We study the extracellular signature [the extracellular AP (EAP)] generated by such a dipole. First, we demonstrate the formation of the dipole and its extracellular signature in detailed morphological models of a reconstructed pyramidal neuron. Then, we study the EAP waveform and its spatial dependence in models with axonal AP initiation and contrast it with the EAP obtained in models with somatic AP initiation. We show that in the models with axonal AP initiation the dipole forms between somatodendritic compartments and the AIS, and not between soma and dendrites as in the classical models. The soma-dendrites dipole is present only in models with somatic AP initiation. Our study has consequences for interpreting extracellular recordings of single-neuron activity and determining electrophysiological neuron types, but also for better understanding the origins of the high-frequency macroscopic extracellular potentials recorded in the brain.
动作电位（APs）是在细胞内和细胞外都能记录到的电现象。APs 通常在轴突的短段，即轴突起始段（AIS）中起始。最近有人提出，在 AP 起始时，胞体和 AIS 形成偶极子。我们研究了这种偶极子产生的细胞外特征[细胞外 AP（EAP）]。首先，我们在重建的锥体神经元的详细形态模型中证明了偶极子的形成及其细胞外特征。然后，我们研究了具有轴突 AP 起始的模型中的 EAP 波形及其空间依赖性，并将其与在具有体 AP 起始的模型中获得的 EAP 进行对比。我们表明，在具有轴突 AP 起始的模型中，偶极子形成于胞体树突区室和 AIS 之间，而不是像经典模型中那样形成于胞体和树突之间。只有在具有体 AP 起始的模型中才存在胞体-树突偶极子。我们的研究对解释单神经元活动的细胞外记录和确定电生理学神经元类型具有重要意义，也有助于更好地理解大脑中记录到的高频宏观细胞外电位的起源。
