McManus O B, Blatz A L, Magleby K L
Department of Physiology and Biophysics, University of Miami School of Medicine, FL 33101.
Pflugers Arch. 1987 Nov;410(4-5):530-53. doi: 10.1007/BF00586537.
(1) Analysis of the durations of open and shut intervals measured from single channels currents provides a means to investigate the mechanisms of channel gating. Durations of open and shut intervals are conveniently measured from single channel data by using a threshold level to indicate transitions between open and shut states. This paper presents a detailed characterization of sampling, binning, and noise errors associated with 50% threshold analysis, provides criteria to reduce these errors, methods to correct for them, and presents an efficient means of data handling for binning and plotting interval durations. (2) Measuring interval durations by sampling at a fixed rate introduces two types of errors, (a) the number of intervals of a given measured duration are increased (promoted) over that expected in the absence of sampling, producing a sampling promotion error, (b) sampling decreases the total fraction of true intervals that are detected, producing a sampling detection error. Sampling errors can be reduced to negligible levels if the actual or effective (after interpolation) sampling period is less than 10-20% of both the dead time and fastest time constant in the distribution of intervals. Dead time is given by the duration of a true interval that has a filtered amplitude equal to 50% of the true amplitude. (3) Methods are presented to correct for sampling promotion error during least squares and maximum likelihood fitting. Sampling detection error is more difficult to correct, but an empirical description of the sampling detection error can be used to calculate the effective fraction of detected events with sampling. (4) Noise in the single channel current record can produce two types of error. (a) If noise peaks in the absence of channel activity exceed the threshold for detection, then false channel events of brief duration are produced. Sufficient filtering will prevent this type of error. (b) Noise can also increase the total fraction of true intervals that are detected, producing a noise detection error. Increased filtering over that required to prevent false events is not necessarily the best method for reducing noise detection error, as increased filtering can prevent detection of the faster exponential components. (5) Noise detection error can be reduced in two ways: (a) an empirical description of the noise detection error can be used to calculate the effective fraction of detected events in the presence of noise. (b) The sampling period can be selected so that the sampling detection error cancels the noise detection error.(ABSTRACT TRUNCATED AT 400 WORDS)
（1）对从单通道电流测量得到的开放和关闭间隔的持续时间进行分析，提供了一种研究通道门控机制的方法。通过使用阈值水平来指示开放和关闭状态之间的转变，可以方便地从单通道数据中测量开放和关闭间隔的持续时间。本文详细描述了与50%阈值分析相关的采样、分箱和噪声误差，提供了减少这些误差的标准、校正这些误差的方法，并提出了一种用于分箱和绘制间隔持续时间的高效数据处理方法。（2）以固定速率采样来测量间隔持续时间会引入两种类型的误差：（a）给定测量持续时间的间隔数量比在无采样情况下预期的数量增加（促进），产生采样促进误差；（b）采样会降低检测到的真实间隔的总比例，产生采样检测误差。如果实际或有效（插值后）采样周期小于间隔分布中死时间和最快时间常数的10%-20%，采样误差可降低到可忽略不计的水平。死时间由具有滤波幅度等于真实幅度50%的真实间隔的持续时间给出。（3）提出了在最小二乘法和最大似然拟合过程中校正采样促进误差的方法。采样检测误差更难校正，但采样检测误差的经验描述可用于计算采样时检测到的事件的有效比例。（4）单通道电流记录中的噪声会产生两种类型的误差：（a）如果在无通道活动时噪声峰值超过检测阈值，则会产生短暂持续时间的假通道事件。充分滤波可防止此类误差。（b）噪声还会增加检测到的真实间隔的总比例，产生噪声检测误差。超过防止假事件所需的滤波增加不一定是减少噪声检测误差的最佳方法，因为增加滤波会阻止更快指数成分的检测。（5）噪声检测误差可通过两种方式降低：（a）噪声检测误差的经验描述可用于计算存在噪声时检测到的事件的有效比例。（b）可以选择采样周期，使采样检测误差抵消噪声检测误差。（摘要截断于400字）
