局部场电位

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Local field potentials (LFP) are transient electrical signals generated in nervous and other tissues by the summed and synchronous electrical activity of the individual cells (e.g. neurons) in that tissue. LFP are "extracellular" signals, meaning that they are generated by transient imbalances in ion concentrations in the spaces outside the cells, that result from cellular electrical activity. LFP are 'local' because they are recorded by an electrode placed nearby the generating cells. As a result of the Inverse-square law, such electrodes can only 'see' potentials in spatially limited radius. They are 'potentials' because they are generated by the voltage that results from charge separation in the extracellular space. They are 'field' because those extracellular charge separations essentially create a local electric field. LFP are typically recorded with a high-impedance microelectrode placed in the midst of the population of cells generating it. They can be recorded, for example, via a microelectrode placed in the brain of a human or animal subject, or in an in vitro brain thin slice.

局部场电位（Local Field Potential, LFP）是神经组织或其他组织中，由细胞电活动的叠加和同步而产生的瞬时电信号，常见于神经元细胞等。局部场点位是由其他细胞电活动导致的瞬时离子浓度差而产生的“胞外”信号。局部场点位也是被置于电活动细胞附近的电极记录下来的“局部”信号，由平方反比定律（Inverse-square Law）易知，电极只能在有限的半径范围内记录到电位信号。局部场点位还是一种“电势”，因为它们也依赖于细胞外液中电荷分离产生的电压。局部场点位更是一种“场”，因为细胞外液中电荷分离本质上创造了一个局部电场。LFP 通常用一个高阻抗微电极记录在产生它的细胞群中间。例如，可以通过放置在人或动物大脑中的微电极，或者放置在体外大脑薄片中来记录它们。

= 背景 =

During local field potential recordings, a signal is recorded using an extracellular microelectrode placed sufficiently far from individual local neurons to prevent any particular cell from dominating the electrophysiological signal. This signal is then low-pass filtered, cut off at ~300 Hz, to obtain the local field potential (LFP) that can be recorded electronically or displayed on an oscilloscope for analysis. The low impedance and positioning of the electrode allows the activity of a large number of neurons to contribute to the signal. The unfiltered signal reflects the sum of action potentials from cells within approximately 50-350 μm from the tip of the electrode and slower ionic events from within 0.5–3 mm from the tip of the electrode. The low-pass filter removes the spike component of the signal and passes the lower frequency signal, the LFP.

During local field potential recordings, a signal is recorded using an extracellular microelectrode placed sufficiently far from individual local neurons to prevent any particular cell from dominating the electrophysiological signal. This signal is then low-pass filtered, cut off at ~300 Hz, to obtain the local field potential (LFP) that can be recorded electronically or displayed on an oscilloscope for analysis. The low impedance and positioning of the electrode allows the activity of a large number of neurons to contribute to the signal. The unfiltered signal reflects the sum of action potentials from cells within approximately 50-350 μm from the tip of the electrode and slower ionic events from within 0.5–3 mm from the tip of the electrode. The low-pass filter removes the spike component of the signal and passes the lower frequency signal, the LFP.

在局部场电位记录过程中，通过放置在离单个局部神经元足够远的细胞外微电极来记录信号，以防止任何特定的细胞控制电生理信号。然后对这个信号进行低通滤波，在约300赫兹处切断，以获得可以用电子方式记录或在示波器上显示以供分析的局部场电位(LFP)。低阻抗和定位的电极允许大量的神经元的活动贡献信号。未经滤波的信号反映了距离电极尖端约50-350微米的细胞的动作电位和距离电极尖端0.5-3毫米的慢离子事件的总和。低通滤波器去除了信号的尖峰分量，并通过低频信号 LFP。

The voltmeter or analog-to-digital converter to which the microelectrode is connected measures the electrical potential difference (measured in volts) between the microelectrode and a reference electrode. One end of the reference electrode is also connected to the voltmeter while the other end is placed in a medium which is continuous with, and compositionally identical to the extracellular medium. In a simple fluid, with no biological component present, there would be slight fluctuations in the measured potential difference around an equilibrium point, this is known as the thermal noise. This is due to the random movement of ions in the medium and electrons in the electrode. However, when placed in neural tissue the opening of an ion channel results in the net flow of ions into the cell from the extracellular medium, or out of the cell into the extracellular medium. These local currents result in larger changes in the electrical potential between the local extracellular medium and the interior of the recording electrode. The overall recorded signal thus represents the potential caused by the sum of all local currents on the surface of the electrode.

The voltmeter or analog-to-digital converter to which the microelectrode is connected measures the electrical potential difference (measured in volts) between the microelectrode and a reference electrode. One end of the reference electrode is also connected to the voltmeter while the other end is placed in a medium which is continuous with, and compositionally identical to the extracellular medium. In a simple fluid, with no biological component present, there would be slight fluctuations in the measured potential difference around an equilibrium point, this is known as the thermal noise. This is due to the random movement of ions in the medium and electrons in the electrode. However, when placed in neural tissue the opening of an ion channel results in the net flow of ions into the cell from the extracellular medium, or out of the cell into the extracellular medium. These local currents result in larger changes in the electrical potential between the local extracellular medium and the interior of the recording electrode. The overall recorded signal thus represents the potential caused by the sum of all local currents on the surface of the electrode.

微电极所连接的电压表或模拟数字转换器测量微电极和参比电极之间的电位差(以伏特计)。参比电极的一端也连接到电压表，而另一端则置于与细胞外介质相同的连续介质中。在一种没有生物成分的简单流体中，测量到的平衡点周围的电位差会有轻微的波动，这就是所谓的热噪声。这是由于离子在介质中的随机运动和电极中的电子。然而，当放置在神经组织中时，离子通道的开放导致离子从细胞外液流入细胞内，或从细胞外液流出细胞进入细胞外液。这些局部电流导致局部细胞外介质和记录电极内部之间的电位发生较大的变化。因此，总的记录信号表示由电极表面所有局部电流之和引起的电位。

= 同步输入 =

The local field potential is believed to represent the synchronised input into the observed area, as opposed to the spike data, which represents the output from the area. In the LFP, high-frequency fluctuations in the potential difference are filtered out, leaving only the slower fluctuations. The fast fluctuations are mostly caused by the short inward and outward currents of action potentials, while the direct contribution of action potentials is minimal in the LFP. The LFP is thus composed of the more sustained currents in the tissue, such as the synaptic and somato-dendritic currents. Data-driven models have shown a predictive relationship between the LFPs and spike activity. The major slow currents involved in generating the LFP are believed to be the same that generate the postsynaptic potential (PSP). It was originally thought that EPSPs and IPSPs were the exclusive constituents of LFPs, but phenomena unrelated to synaptic events were later found to contribute to the signal (Kobayashi 1997).

The local field potential is believed to represent the synchronised input into the observed area, as opposed to the spike data, which represents the output from the area. In the LFP, high-frequency fluctuations in the potential difference are filtered out, leaving only the slower fluctuations. The fast fluctuations are mostly caused by the short inward and outward currents of action potentials, while the direct contribution of action potentials is minimal in the LFP. The LFP is thus composed of the more sustained currents in the tissue, such as the synaptic and somato-dendritic currents. Data-driven models have shown a predictive relationship between the LFPs and spike activity. The major slow currents involved in generating the LFP are believed to be the same that generate the postsynaptic potential (PSP). It was originally thought that EPSPs and IPSPs were the exclusive constituents of LFPs, but phenomena unrelated to synaptic events were later found to contribute to the signal (Kobayashi 1997).

局部场势被认为代表同步输入到观测区域，而不是代表区域输出的尖峰数据。在 LFP 中，电位差的高频波动被过滤掉，只留下较慢的波动。动作电位的快速波动主要是由动作电位的短向内和短向外电流引起的，而在 LFP 中动作电位的直接贡献是最小的。因此，LFP 是由组织中更持续的电流组成的，如突触电流和树突电流。数据驱动的模型已经显示了 LFPs 和穗活动之间的预测关系。产生 LFP 的主要慢电流被认为与产生突触后电位(PSP)的电流相同。最初认为 EPSPs 和 IPSPs 是 LFPs 的唯一成分，但后来发现与突触事件无关的现象促成了信号(Kobayashi，1997年)。

= 几何排列 =

Which cells contribute to the slow field variations is determined by the geometric configuration of the cells themselves. In some cells, the dendrites face one direction and the soma another, such as the pyramidal cells. This is known as an open field geometrical arrangement. When there is simultaneous activation of the dendrites a strong dipole is produced. In cells where the dendrites are arranged more radially, the potential difference between individual dendrites and the soma tend to cancel out with diametrically opposite dendrites, this configuration is called a closed field geometrical arrangement. As a result the net potential difference over the whole cell when the dendrites are simultaneously activated tends to be very small. Thus changes in the local field potential represent simultaneous dendritic events in cells in the open field configuration.

Which cells contribute to the slow field variations is determined by the geometric configuration of the cells themselves. In some cells, the dendrites face one direction and the soma another, such as the pyramidal cells. This is known as an open field geometrical arrangement. When there is simultaneous activation of the dendrites a strong dipole is produced. In cells where the dendrites are arranged more radially, the potential difference between individual dendrites and the soma tend to cancel out with diametrically opposite dendrites, this configuration is called a closed field geometrical arrangement. As a result the net potential difference over the whole cell when the dendrites are simultaneously activated tends to be very small. Thus changes in the local field potential represent simultaneous dendritic events in cells in the open field configuration.

哪些细胞促成了慢场变化是由细胞本身的几何结构决定的。在某些细胞中，树突面向一个方向，而胞体面向另一个方向，如锥体细胞。这就是所谓的开场几何排列。当树枝晶同时被激活时，一个强大的偶极子就产生了。在树突呈放射状排列的细胞中，单个树突和胞体之间的电位差倾向于与完全相反的树突相互抵消，这种结构被称为封闭场几何排列。因此，当树突同时被激活时，整个细胞的净电位差趋于很小。因此，局部场电位的变化代表了开放场构型中细胞内同时发生的树突事件。

= 细胞外液低通滤波 =

Part of the low-pass filtering giving rise to local field potentials is due to complex electrical properties of extracellular space. The fact that the extracellular space is not homogeneous, and composed of a complex aggregate of highly conductive fluids and low-conductive and capacitive membranes, can exert strong low-pass filtering properties. Ionic diffusion, which plays an important role in membrane potential variations, can also act as a low-pass filter.

Part of the low-pass filtering giving rise to local field potentials is due to complex electrical properties of extracellular space. The fact that the extracellular space is not homogeneous, and composed of a complex aggregate of highly conductive fluids and low-conductive and capacitive membranes, can exert strong low-pass filtering properties. Ionic diffusion, which plays an important role in membrane potential variations, can also act as a low-pass filter.

引起局域场势的低通滤波部分是由于细胞外液的复杂电学性质。事实上，细胞外液是不均匀的，由高导电性流体和低导电性和电容性薄膜组成的复杂聚合物，可以发挥强大的低通过滤性能。离子扩散在膜电位变化中起着重要作用，也可以作为低通滤波器。

External links

• Mechanisms of local field potentials (Scholarpedia)

• Mechanisms of local field potentials (Scholarpedia)

= = 外部链接 =

• 本地场势机制(Scholarpedia)

Category:Electrophysiology Category:Action potentials

类别: 电生理学类别: 动作电位

This page was moved from wikipedia:en:Local field potential. Its edit history can be viewed at 局部场电位/edithistory