Frequency analysis of gut EMG.

The EMG of the gut smooth muscle plays an important role in the regulation of gastrointestinal motility in health and disease. The EMG in general consists of an omnipresent oscillatory electrical control activity (ECA) and spikes or other potentials that result in contractions of the smooth muscle. This paper addresses the question of how the ECA signals can best be processed and how inappropriate transformations of such signals may produce misleading results. The various factors affecting the composition of the gut EMG, in time and space along the gut, are discussed briefly. The need for the analysis of the ECA for its oscillatory nature is mentioned together with details regarding the widely used visual, period, and Fourier analysis techniques. Fourier analysis techniques have been applied with increasing frequency to gut EMG; the various features of Fourier analysis and considerations for their implementation on the computer are discussed. The visual, period, and Fourier analysis approaches as well as their uses and limitations in application to a variety of ECAs of the stomach and of the colon in dogs and humans are illustrated. This study indicates that period analysis techniques are well suited for the study of the visibly oscillatory upper gut EMG, while smoothed spectral analysis is more appropriate for the study of colonic EMG.