Shifman Aaron R, Longtin André, Lewis John E
Department of Biology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
Center for Neural Dynamics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
Sci Rep. 2015 Oct 30;5:15780. doi: 10.1038/srep15780.
Identifying and understanding the current sources that give rise to bioelectric fields is a fundamental problem in the biological sciences. It is very difficult, for example, to attribute the time-varying features of an electroencephalogram recorded from the head surface to the neural activity of specific brain areas; model systems can provide important insight into such problems. Some species of fish actively generate an oscillating (c. 1000 Hz) quasi-dipole electric field to communicate and sense their environment in the dark. A specialized electric organ comprises neuron-like cells whose collective signal underlies this electric field. As a step towards understanding the detailed biophysics of signal generation in these fish, we use an anatomically-detailed finite-element modelling approach to reverse-engineer the electric organ signal over one oscillation cycle. We find that the spatiotemporal profile of current along the electric organ constitutes a travelling wave that is well-described by two spatial Fourier components varying in time. The conduction velocity of this wave is faster than action potential conduction in any known neuronal axon (>200 m/s), suggesting that the spatiotemporal features of high-frequency electric organ discharges are not constrained by the conduction velocities of spinal neuron pathways.
识别和理解当前产生生物电场的源头是生物科学中的一个基本问题。例如，很难将从头部表面记录的脑电图的时变特征归因于特定脑区的神经活动；模型系统可以为这类问题提供重要的见解。某些鱼类会主动产生一个振荡（约1000赫兹）的准偶极电场，以便在黑暗中进行交流和感知周围环境。一个专门的电器官由类似神经元的细胞组成，这些细胞的集体信号构成了这个电场的基础。作为理解这些鱼类信号产生详细生物物理学的第一步，我们使用一种解剖学上详细的有限元建模方法，在一个振荡周期内对电器官信号进行逆向工程。我们发现，沿着电器官的电流时空分布构成了一个行波，该行波可以由两个随时间变化的空间傅里叶分量很好地描述。这个波的传导速度比任何已知神经元轴突中的动作电位传导速度都要快（>200米/秒），这表明高频电器官放电的时空特征不受脊髓神经元通路传导速度的限制。
