Notes on the Analysis and Interpretation of Electrical Signals
One of the biggest problems encountered by investigators who are beginners in electrophysiology is the interpretation of results. Often the first aspect of the problem centers on whether the output of whatever read-out device is used is, indeed, related to biological phenomena. Therefore, one of the first considerations is to determine whether the output signals are biological phenomena related to the experiment or some sort of artifact. This sounds fundamental, but it cannot be overstressed. One thing that will be extremely helpful if it is constantly in mind is the analysis of the axes of the read-out device. The approach of electrophysiology is fundamentally to make an electrographic analysis or recording. Consequently, whether one uses a CRO, a camera, digital voltmeter, or tape recorder, one axis (usually the vertical) is always a voltage axis. In addition, since most signals vary as a function of time, the other axis is a time axis. Again, most instruments are set up such that the horizontal axis is a time axis, but a digital voltmeter, of course, would be an exception. Since we have the two axes (voltage and time) as an output, the first consideration is to examine the signal critically with respect to these two parameters. Does the output make sense? Even the novice investigator has a good idea of the amplitude and temporal dimensions of the signals he expects to find. Therefore, a critical examination of the voltage and time axes will help determine whether the signal is reasonable for the experimental conditions. It is not by accident that editors demand clearly labelled axes on electrographic records published in their journals.
KeywordsTime Axis Biological Phenomenon Compound Action Potential Electric Fish Digital Voltmeter
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