Modeling extracellular field potentials and the frequency-filtering properties of extracellular space
Modeling extracellular field potentials and the frequency-filtering properties of extracellular space
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DOI：
10.1016/s0006-3495(04)74250-2
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发表时间：
2004-03-01
影响因子：
3.4
通讯作者：
Destexhe, A
中科院分区：
文献类型：
--
作者：
Bédard, C;Kröger, H;Destexhe, A
细胞外局部场电位通常被建模为由嵌入均匀细胞外介质中的一组电流源产生。虽然这种形式主义可以成功地模拟几个属性的细胞外局部场电位，它不占其频率依赖性衰减与距离，正确地建模细胞外尖峰的属性。在这里，我们推导出的细胞外电位，包括这种频率依赖性衰减的表达式。我们首先表明，如果细胞外电导率是非均匀的，有诱导的非均匀的电荷密度，可能会导致低通滤波器。接下来，我们推导出一个简化的模型，包括一个点状（或球形）的电流源与球对称concluctivity/介电常数梯度的源周围。我们分析了不同的径向剖面的电导率和介电常数的频率滤波行为的这个模型的效果。我们发现，这个简单的模型一般显示低通滤波行为，其中快速电事件（如Na+介导的动作电位）衰减非常陡峭的距离，而较慢（K+介导的）事件传播在细胞外空间更大的距离，定性与实验观察。这个简单的模型可以用来获得频率依赖性的胞外场电位，而不考虑明确的细胞外空间的复杂折叠。
Extracellular local field potentials are usually modeled as arising from a set of current sources embedded in a homogeneous extracellular medium. Although this formalism can successfully model several properties of extracellular local field potentials, it does not account for their frequency-dependent attenuation with distance, a property essential to correctly model extracellular spikes. Here we derive expressions for the extracellular potential that include this frequency-dependent attenuation. We first show that, if the extracellular conductivity is nonhomogeneous, there is induction of nonhomogeneous charge densities that may result in a low-pass filter. We next derive a simplified model consisting of a punctual (or spherical) current source with spherically symmetric concluctivity/permittivity gradients around the source. We analyze the effect of different radial profiles of conductivity and permittivity on the frequency-filtering behavior of this model. We show that this simple model generally displays low-pass filtering behavior, in which fast electrical events (such as Na+-mediated action potentials) attenuate very steeply with distance, whereas slower (K+-mediated) events propagate over larger distances in extracellular space, in qualitative agreement with experimental observations. This simple model can be used to obtain frequency-dependent extracellular field potentials without taking into account explicitly the complex folding of extracellular space.