Autonomic indexes during the vestibular-visual conflict exposure: a squirrel monkey study.

To assess the dynamic changes of the autonomic neural responses evoked by vestibular-visual conflict (VVC) in the squirrel monkey, we analyzed the changes of salivary amount and sodium concentration, and the coefficient of variance (CV) of R-R intervals (RRI) along the time course of VVC exposure given in pitch plane. The sodium concentration and the amount of saliva showed clear increases at the first and second 15 min stimulation periods. The CV of RRI was found to increase over the entire periods of stimulation, and there was a significant difference between the rest value and those in stimulated periods. The correlation between the CV of RRI, and amount of salivation was highly positive. These results indicate the existence of a common pattern of autonomic neural response during VVC, and suggest usefulness of these indexes for objectively monitoring the severity of motion sickness.