What is measured in electrogastrography?

The object of this study was to elucidate what is actually measured in electrogastrography. Comparison of gastric signals simultaneously recorded from serosal and cutaneous electrodes in the conscious dog led to the following findings: 1. In the absence of phasic contractile activity and electrical response activity (ERA), the cutaneous recordings contained a frequency corresponding to the fundamental frequency of the electrical control activity (ECA) of the stomach (about 0.08 Hz). 2. Tachygastrias gave rise to cutaneous signals containing the tachygastric frequency (about 0.25 Hz). 3. The amplitude of the electrogastrogram increased when ERA occurred. It is concluded that both ECA and ERA are reflected in the electrogastrogram. A model is proposed that describes the electrogastrogram as the result of field potentials generated by depolarization and repolarization dipoles.