PWE-051 Studies of the psychophysiological markers and the brain processing of nausea in healthy humans using a novel virtual reality video

Abstract

Objective: psychophysiological markers of nausea that also predict nausea susceptibility in humans are lacking. The regions of the human brain that process the sensation of nausea are poorly characterized thus a novel model of motion sickness induced nausea was used. A 10-min video of motion video (MV) and a control (still) were presented to 98 healthy volunteers (age 26 +/- 8 years, 53 male). We monitored sympathetic activity [heart rate (HR) and mean, systolic and diastolic blood pressure (MBP, SBP and DBP)]; parasympathetic activity [cardiac vagal tone (CVT), cardiac sensitivity to baroreceptor reflex (CSB)], electrogastrogram (EGG) and blood cortisol. 25 nausea susceptible (NS,) was compared with 25 nausea resistant (NR, no nausea) subjects. 17 NS and 11 NR (aged 25 +/- 5 years) repeated the experiments with Functional Magnetic Resonance Imaging to assess brain activity. All subjects completed the studies without vomiting. Comparison of MV to control: MV raised nausea scores (+57%+/-11, P < 0.01, range 0-300%) and anxiety scores (Spielberger state anxiety inventory, +35%+/-5, P < 0.01). MV also raised cardiac sympathetic (HR, SBP, DBP, and MBP) and reduced parasympathetic activity (CVT and CSB) (Table 1). Comparison of NS with NR: the NS subjects showed more parasympathetic withdrawal; larger sympathetic activation and higher cortisol release and EGG dysrrhythmia in comparison to NR subjects (Table 1). Brain imaging data (all results had corrected P < 0.05): There was positive correlation between brain activity and nausea level in the inferior frontal gyrus; and negative correlation in declive, culmen, cuneus, and parahippocampal gyrus in NS. Compared to NR, NS subjects showed increased activity in the substania nigra; and decreased activity in declive and parahippocampal gyrus during nausea. NS subjects decreased PNS tone and increased EGG dysrrhythmia, SNS tone, anxiety and cortisol, and showed different brain processing patterns compared to NR suggesting these parameters could be used as markers of nausea susceptibility. Thus, this model is safe and effective in inducing nausea without vomiting and can be used to study effects of nausea on GI function together with (Table Presented) correlations with objective physiological and brain activity markers. The comprehensive markers identified need to be reverse translated to animal experiments.