Error analysis of Cm measurement under the whole-cell patch-clamp recording

We present a method for analysing propagation errors in membrane capacitance (Cm) measurements under the whole-cell patch-clamp configuration, which mainly focusses on errors in Cm estimates due to the ‘residual’ fast capacitance (ΔCp). The method employs a quasi-phasor diagram for visualisation of the analysis. Our results show that both under- and over-compensation of fast capacitance will cause errors in Cm, and errors in the magnitude and in the phase angle of cell admittance make their respective and opposite contributions to propagation errors in Cm. Within optimal frequencies, over-compensation of fast capacitance will cause a smaller propagation error in Cm and produce more accurate Cm estimates than under-compensation of fast capacitance will do. Information about how other cell parameters, such as smaller series resistance, baseline Cm value and the stimulus frequency, change the total error in Cm due to ΔCp is also provided. Guidelines for accurate Cm recordings are given to make it easy for users to perform their own error analysis.