Differences in autonomic responses between subjects with and without nausea while watching an irregularly oscillating video

Prodromal signs such as cardiac rhythm disturbance and changes in gastric motility are generally induced before and during nausea in humans. These autonomic reactions were compared in subjects who were or were not experiencing nausea. Nausea was induced by having the subjects view a movie of oscillating pictures. Seventeen healthy volunteers were asked to relax their muscles and watch the movie. Electrogastrogram (EGG), electrocardiogram (ECG), palmar and metopic perspiration, digital blood flow and thoracic movement related to respiration were simultaneously measured while the subjects viewed the movie. A total of 11 of 17 subjects complained of nausea after watching the movie. The characteristic changes in their autonomic responses during exposure to the movie were as follows. The power of the EGG, heart rate and metopic perspiration significantly increased compared to those before watching the movie. The respiratory cycle gradually increased during and even after watching the movie. In contrast, no significant changes in the power of the EGG, heart rate and metopic perspiration were observed in the remaining six subjects who did not experience nausea. The role of the autonomic nervous system in nausea is discussed. These results suggest that these symptoms regarding the sympathetic nervous system could actually be defensive reactions against the sensation of nausea.