Abstract / Summary
Introduction Previous studies have widely used surface electrogastrogram (EGG) signals to non-invasively evaluate gastric motility. However, it focused only on the assessment of electrical activity in a certain stomach region and lacked the analysis of interactions between different gastric regions. In the study, we aimed to assess the correlations of myoelectrical activity between distinct stomach areas using functional connectivity (FC) methods by three-channel EGG for the first time. Methods The study contained 20 healthy subjects and the dataset for each subject consisted of two three-channel EGG signals (labeled as CH1, CH2 and CH3; CH1 projected onto the region of lesser curvature, CH3 projected onto the region of greater curvature, and CH2 positioned the region between CH1 and CH3) with a sampling rate of 2 Hz acquired from three locations of stomach during a 20-minute period of fasting and postprandial states respectively. Firstly, the EGG signals were band-pass filtered into three slow wave (SW) bands by finite impulse response (FIR) filter, namely bradygastria (0.017-0.033 Hz), normogastria (0.033-0.067 Hz) and tachygastria (0.067-0.15 Hz). Secondly, we employed four FC algorithms (i.e. Spearman correlation coefficient (SCC), phase lag index (PLI), mutual information (MI) and coherence (Coh)) to calculate the connection strength of each pair of gastric areas. Finally, the FC strength between fasting and postprandial conditions for all subjects or the normal weight (NW) or overweight (OW) people and between the NW and OW groups for both fasting and postprandial states were compared, respectively. Results The results indicated that compared to the fasting state, lower SCC of CH1 and CH3 in bradygastria for the NW group and significantly increased SCC of CH2 and CH3 in normogastria for all subjects were observed under the postprandial state. The NW group had greater MI of CH1-CH3 in bradygastria and normogastria during the fasting condition relative to the OW group. It was also found that the connections between CH1 and CH3 for Coh in normogastria and tachygastria and for MI in tachygastria and for SCC in normogastria were markedly increased in the normal individuals than those in the OW group under the postprandial state. Moreover, the connections of CH1-CH3 for SCC, MI in normogastria and for Coh in normogastria and tachygastria showed significantly negative correlations with body mass index during the postprandial condition. Discussion The findings of the study demonstrated that the FC techniques can be used as an exploratory analytical approach to assess gastric functional activity, and the FC strength in the NW group were remarkably increased in comparison with the OW group under the postprandial state, suggesting that it should be considered to separately analyze the EGG signals of individuals with normal weight and those who are overweight when conducting the gastric electrical analysis in scientific research or practical clinical practice.