SPIKE INITIATION BY TRANSMEMBRANE CURRENT - WHITE-NOISE ANALYSIS
SPIKE INITIATION BY TRANSMEMBRANE CURRENT - WHITE-NOISE ANALYSIS
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DOI：
10.1113/jphysiol.1976.sp011516
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发表时间：
1976-01-01
影响因子：
5.5
通讯作者：
SEGUNDO, JP
中科院分区：
文献类型：
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作者：
BRYANT, HL;SEGUNDO, JP
使用高斯白噪声刺激检查海兔神经元中与尖峰启动相关的跨膜电流特征。这种刺激的优点是，它以随机顺序呈现大量波形，而无需预先判断其功效，并且可以进行简单的统计计算。用重复的高斯白噪声电流片段进行刺激，显示出受测试神经元的放电时间具有显着的不变性，并表明它们的反应具有高度的可靠性。尖峰触发所涉及的频率（< 5 Hz）忠实地传播了长达几毫米，证明了体内电流注入来检查触发位点的尖峰起始是合理的。对峰值之前的电流波形的检查表明，多种变化都可能是有效的。统计分析包括计算当前值对的概率密度、平均值、标准差和相关系数。每个统计数据都显示为峰值之前时间的函数。尖峰之前的平均电流轨迹是多相的，并且取决于直流偏压的存在和极性。在峰值之前，早期相对较小的向内或向外阶段之后是一个较大的向外阶段。早期阶段倾向于反对直流偏压的极性。平均电流轨迹的后期向外阶段在触发动作电位 (AP) 之前达到最大值 40-75 ms，并在触发时返回到接近零值。 AP 之前出现的电流峰值可能部分是由跨膜电流和电位之间的相位延迟引起的。平均电流轨迹未能在峰值后立即返回到控制值，这证明了下降阶段在尖峰触发中的积极作用。峰值之前的概率密度是高斯分布，表明平均值也是最可能的值。尽管密度很宽，证实了尖峰之前有各种各样的电流波形，但它们的标准偏差相对于对照显着降低，表明尖峰触发中平均电流轨迹的首选状态。电流对之间的相关系数矩阵表明，尖峰往往先于波形，这些波形部分接近平均电流轨迹，部分保留其形状。尖峰诱发时期的平均一阶和二阶导数表明，电流斜率和加速度分别在尖峰触发前的最后 200 毫秒内最为关键，并且这些动态刺激成分对于维持在去极化而非超极化偏差下的细胞更为重要。尖峰触发系统的简单模型由线性滤波器（一阶维纳内核）和带有“死区时间”的阈值设备组成，在预测实验观察到的尖峰时序方面非常准确。许多刺激参数（极性和幅度、变异性、斜率、加速度、时间相关性）与尖峰触发相关，并且对于特定刺激（例如突触后电位），一个特征的缺失可以通过另一个特征的存在来补偿。
Transmembrane current features correlated with spike initiation were examined in Aplysia neurons using a Gaussian white-noise stimulus. This stimulus had the advantages that it presented numerous wave forms in random order without prejudgement as to their efficacies, and that it allowed straightforward statistical calculations. Stimulation with a repeating segment of Gaussian white-noise current revealed remarkable invariance in the firing times of the tested neurons and indicated a high degree of reliability of their response. Frequencies (< 5 Hz) involved in spike triggering propagated faithfully for up to several millimeters, justifying intrasomatic current injection to examine spike initiation at the trigger locus. Examination of current wave forms preceding spikes indicated that a wide variety could be effective. A statistical analysis included computation of probability densities, averages, standard deviations and correlation coefficients of pairs of current values. Each statistic was displayed as a function of time before the spike. The average current trajectory preceding a spike was multiphasic and depended on the presence and polarity of a DC bias. An early, relatively small inward- or outward-going phase was followed by a large outward phase before the spike. The early phase tended to oppose the polarity of the DC bias. The late outward phase of the average current trajectory reached a maximum 40-75 ms before triggering the action potential (AP) and returned to near zero values at the moment of triggering. The current peak occurring in advance of the AP was probably partly caused by a phase delay between the transmembrane current and potential. The failure of the average current trajectory to return to control values immediately following the peak argued for a positive role of the declining phase in spike triggering. Probability densities preceding spikes were Gaussian, indicating that the average was also the most probable value. Although the densities were broad, confirming that spikes were preceded by a wide variety of current wave forms, their standard deviations were reduced significantly with respect to controls, suggesting a preferred status of the average current trajectory in spike triggering. The matrix of correlation coefficients between current pairs suggested that spikes tended to be preceded by wave forms that in part kept close to the average current trajectory and in part preserved its shape. The average 1st and 2nd derivatives of spike-evoking epochs revealed that current slope and acceleration, respectively, were most crucial in the last 200 ms before spike triggering, and that these dynamic stimulus components were more important for a cell maintained under a depolarizing, rather than a hyperpolarizing bias. A simple model of the spike-triggering system, consisting of a linear filter (1st-order Wiener kernel) followed by a threshold device with ''dead-time'', was quite accurate in predicting experimentally observed spike timings. A number of stimulus parameters (polarity and amplitude, variability, slope, acceleration, temporal correlation) were relevant in spike-triggering, and for a particular stimulus (e.g., a postsynaptic potential), the absence of one feature could be compensated for by the presence of another.