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首页> 外文期刊>Journal of Neurophysiology >Characterization of reliability of spike timing in spinal interneurons during oscillating inputs.
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Characterization of reliability of spike timing in spinal interneurons during oscillating inputs.

机译：振荡输入过程中脊神经中枢尖峰定时可靠性的表征。

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摘要

The spike timing in rhythmically active interneurons in the mammalian spinal locomotor network varies from cycle to cycle. We tested the contribution from passive membrane properties to this variable firing pattern, by measuring the reliability of spike timing, P, in interneurons in the isolated neonatal rat spinal cord, using intracellular injection of sinusoidal command currents of different frequencies (0.325-31.25 Hz). P is a measure of the precision of spike timing. In general, P was low at low frequencies and amplitudes (P = 0-0.6; 0-1.875 Hz; 0-30 pA), and high at high frequencies and amplitudes (P = 0.8-1; 3.125-31.25 Hz; 30-200 pA). The exact relationship between P and amplitude was difficult to describe because of the well-known low-pass properties of the membrane, which resulted in amplitude attenuation of high-frequency compared with low-frequency command currents. To formalize the analysis we used a leaky integrate and fire (LIF) model with a noise term added. The LIF model was able to reproduce the experimentally observed properties of P as well as the low-pass properties of the membrane. The LIF model enabled us to use the mathematical theory of nonlinear oscillators to analyze the relationship between amplitude, frequency, and P. This was done by systematically calculating the rotational number, N, defined as the number of spikes divided by the number of periods of the command current, for a large number of frequencies and amplitudes. These calculations led to a phase portrait based on the amplitude of the command current versus the frequency-containing areas [Arnold tongues (ATs)] with the same rotational number. The largest ATs in the phase portrait were those where N was a whole integer, and the largest areas in the ATs were seen for middle to high (>3 Hz) frequencies and middle to high amplitudes (50-120 pA). This corresponded to the amplitude- and frequency-evoked increase in P. The model predicted that P would be high when a cell responded with an integer and constant N. This prediction was confirmed by comparing N and P in real experiments. Fitting the result of the LIF model to the experimental data enabled us to estimate the standard deviation of the internal neuronal noise and to use these data to simulate the relationship between N and P in the model. This simulation demonstrated a good correspondence between the theoretical and experimental values. Our data demonstrate that interneurons can respond with a high reliability of spike timing, but only by combining fast and slow oscillations is it possible to obtain a high reliability of firing during rhythmic locomotor movements. Theoretical analysis of the rotation number provided new insights into the mechanism for obtaining reliable spike timing.
机译：在哺乳动物的脊髓运动网络中，有节奏地活跃的中间神经元的高峰时间随周期而变化。我们通过细胞内注射不同频率（0.325-31.25 Hz）的正弦指令电流，通过测量新生鼠脊髓中神经元的尖峰正时P的可靠性，测试了被动膜特性对这种可变激发模式的贡献。 。 P是尖峰定时精度的度量。通常，P在低频和幅值较低时（P = 0-0.6; 0-1.875 Hz; 0-30 pA），而在高频和幅值较高时（P = 0.8-1; 3.125-31.25 Hz; 30- 200 pA）。由于膜的众所周知的低通特性，P和幅度之间的确切关系难以描述，与低频指令电流相比，这导致了高频的幅度衰减。为了使分析正式化，我们使用了泄漏积分和火灾（LIF）模型并添加了噪声项。 LIF模型能够重现实验观察到的P特性以及膜的低通特性。 LIF模型使我们能够使用非线性振荡器的数学理论来分析幅度，频率和P之间的关系。这是通过系统地计算旋转数N（定义为尖峰数除以周期数）来完成的。指令电流，用于大量的频率和振幅。这些计算导致了基于指令电流的幅度相对于具有相同转数的含频率区域[阿诺德舌头（AT）]的相像。相图中最大的AT是N是一个整数的AT，并且AT中最大的区域是中高（> 3 Hz）频率和中高振幅（50-120 pA）。这对应于P的振幅和频率诱发的增加。该模型预测，当细胞以整数和常数N响应时，P会很高。通过在实际实验中比较N和P可以证实这一预测。将LIF模型的结果拟合到实验数据使我们能够估计内部神经元噪声的标准偏差，并使用这些数据来模拟模型中N和P之间的关系。该模拟表明理论值与实验值之间具有良好的对应关系。我们的数据表明，内部神经元可以以高可靠性的尖峰定时响应，但是只有通过组合快速振荡和慢速振荡，才有可能在节律运动中获得高可靠性的点火。转数的理论分析为获得可靠的尖峰定时提供了新的见解。

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