Adjustments for the display of quantized ion channel dwell times in histograms with logarithmic bins

Dwell-time histograms are often plotted as part of patch-clamp investigatio ns of ion channel currents. The advantages of plotting these histograms wit h a logarithmic time axis were demonstrated by Blatz and Magleby (1986, J. Physiol (Lond.). 378.141-174), McManus et at. (1987, Pflugers Arch. 410:530 -553), and Sigworth and Sine (1987, Biophys. J. 52:1047-1054). Sigworth and Sine argued that the interpretation of such histograms is simplified if th e counts are presented in a manner similar to that of a probability density function. However, when ion channel records are recorded as a discrete tim e series, the dwell times are quantized. As a result, the mapping of dwell times to logarithmically spaced bins is highly irregular; bins may be empty , and significant irregularities may extend beyond the duration of 100 samp les. Using simple approximations based on the nature of the binning process and the transformation rules for probability density functions, we develop adjustments for the display of the counts to compensate for this effect. T ests with simulated data suggest that this procedure provides a faithful re presentation of the data.