Nausea is an unpleasant experience characterised by a range of gastric, cardiac, psychological and sopite symptoms. The brain processing of nausea is poorly understood. A number of factors have been proposed to influence an individual’s experience of nausea, including age, gender, autonomic nervous system (ANS) and neuroanatomy; including how these factors interact at the brain level. Moreover, some individuals are significantly more susceptible to nausea than others, which we hypothesised could be attributed to differences in brain structure. We aimed to address this knowledge gap by studying subcortical brain morphology in subjects of varying sensitivities to nausea induced by motion sickness.Methods
28 healthy subjects were included in this analysis (15 males; mean age 24 years), all of whom had resting parasympathetic cardiac vagal tone (CVT) and sympathetic cardiac sympathetic index (CSI) quantified. Subjects were exposed to a validated 10 min motion video, during which they rated their severity of nausea. All underwent high-resolution structural MRI and Bayesian vertex analysis was performed to segment subcortical nuclei and investigate shape changes associated with nausea susceptibility.Results
Increasing nausea scores were positively correlated with shape alterations of the left amygdala, right caudate and bilateral putamen, when regressed for CVT, age, and gender (Figure 1) (all FWER-corrected p<0.05). Interestingly however, with alternate regression analysis for CSI, age and gender, these morphological deformation changes became non-significant, suggestive that the aforementioned significant results are sympathetic-driven nausea-susceptibility changes.Conclusion
Susceptibility to nausea is associated with subcortical nuclei morphology. We illustrate a strong association between the ANS and these structural differences. Given these morphological changes are arguably sympathetic-driven, future research should investigate methods to modulate autonomic tone via these nuclei, in order to establish therapies to diminish nausea susceptibility.