Effect of Lying on Gastric Electrical Rhythm

Abstract

Purpose: The gastrointestinal tract is uniquely sensitive to mental stress, reflecting the communication between the central nervous system and the enteric nervous system. We hypothesized that this relationship could be exploited to provide insight into the psychological state of an individual when lying by analyzing changes in gastric physiology. Current lie detection methods (using standard polygraph) rely on non- GI physiological changes (ie. heart rate and sweating), but are only about 90% accurate and often unreliable. Methods: Sixteen healthy volunteers (13F, 3M) were recruited. Simultaneous electrogastrogram “EGG” and electrocardiogram “EKG” recordings were done for 3 periods, Baseline “BsL”, “Lying” and “Truth”; the later 2 being randomized. Autonomic activity was assessed via spectral analysis of heart rate variability (HRV) data derived from EKG. Gastric slow waves were assessed via spectral analysis of EGG signal. Statistical analysis was done using Student t-test and ANOVA as appropriate. Results: The 2nd channel of EGG, located on stomach proximal antral area, showed a significant decrease in% normal slow wave in Lying vs. BsL (75.39 ± 5.5 vs. 82.29 ± 4.47; P = 0.04). This may be attributed to significant increase in% arrhythmia in Lying vs. BsL (11.13 ± 3.87 vs. 6.35 ± 2.86; P = 0.02). HRV analysis showed a significant increase in average heart rate in Lying and Truth vs. BsL (75.76 ± 1.73; 74.4 ± 1.69 vs. 72.19 ± 1.43); (p = 0.05, 0.002, 0.001 respectively). There was a significant increase in sympathovagal balance in Lying vs. BsL (1.67 ± 0.33 vs. 1.35 ± 0.32; P = 0.045), which might be attributed to significant decrease in vagal activity in both Lying and Truth periods vs. BsL (0.32 ± 0.04 and 0.33 ± 0.04 vs. 0.4 ± 0.04; P = 0.026 and 0.003 respectively). Conclusions: Lying and truth telling are both associated with an increase in heart rate and sympathovagal balance. However, the act of lying is associated with a significant increase in gastric arrhythmia. Thus standard polygraph methods to assess heart rate variability may not perform as well as the EGG in distinguishing between lying and telling the truth. The addition of the EGG to standard polygraph methods has clear value in improving the accuracy of current lie detectors. In addition to a new, potentially breakthrough method for a variety of security applications, the results also provide understanding of the complex communication between the big brain and the little brain in the stomach. Further research in real-life situations and using larger numbers is necessary to validate these results.