In normal subjects, the gastric electrical activity (GEA) consists of a 3 cycle-per-minute slow wave known as the , electrical control activity (ECA). While cutaneous electrodes placed on the surface of the abdomen can record GEA, determination of frequency is the only reliable parameter available from the cutaneous electrogastrogram (EGG). The magnetogastrogram (MGG), the measurement of magnetic fields from GEA, may have greater clinical value than the EGG since gastric magnetic fields reflect the smooth muscle ECA more accurately than the EGG. Low-conductivity tissue layers present in the abdomen serve to smooth and attenuate the electric potential from GEA sources, resulting in a cutaneous EGG that is a spatial summation of many different bioelectric sources. The purpose of this project is to characterize normal and abnormal gastric electrical activity by noninvasive examination of the externally-recorded MGG. We hypothesize that GEA produces regular| spatiotemporal magnetic field patterns that characterize the health status of gastric smooth muscle. Whereas healthy gastric smooth muscle is electrically coupled and allows GEA to propagate from the antral pacemaker site toward the pylorus, we hypothesize that disorders that uncouple gastric smooth muscle disrupt the regular GEA propagation patterns. We hypothesize that spatiotemporal patterns in multi-channel MGG recordings will correlate strongly with the underlying GEA and that they will change under abnormal conditions, reflecting the underlying GEA. We will measure normal serosal potentials and magnetic fields and compare these with data from (1) the mechanically divided stomach, (2) GEA released from autonomic vagal influence, (3) pharmacologically-induced gastric dysrhythmias, and (4) patients with diabetic gastroparesis. If successful, our studies will represent the first characterization of biomagnetic signatures of abnormal gastric function. In addition to improving our understanding of the basic science of gastric electrophysiology, these studies will significantly advance our goal to introduce this method as a routine clinical tool, providing physicians with a noninvasive assessment of the function of the stomach.
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