Galvanic Vestibular Stimulation: a new model of placebo-induced nausea

Traditional rotation-based models of placebo nausea are limited because they do not have vehicle settings and are tied to their context. The present study introduces a new model for examining placebo-induced nausea in the laboratory that overcomes these limitations, namely, Galvanic Vestibular Stimulation (GVS). GVS stimulates the vestibular system to cause nausea through sensory mismatch with visual cues and importantly has a non-nauseating placebo setting. Using this, we tested whether conditioning could elicit placebo nausea when participants were later exposed to placebo stimulation as well as whether this placebo nausea was generalised across contexts--something that is extremely difficult to test with rotation-based models of placebo nausea.

Thirty healthy undergraduate students were randomised to receive either placebo GVS (controls) or active GVS during training (Context-Consistent and Context-Change). On test, all groups received placebo GVS. The controls and Context-Consistent groups were tested in the same context as training, whereas the Context-Change group was tested in a new context.

Participants conditioned with nausea during training had significantly higher nausea symptom ratings after placebo stimulation on test than those given no conditioning. This placebo-induced nausea also generalised to a novel test context with no differences observed between the Context-Change and Context-Consistent groups.

GVS provides a new model of placebo-induced nausea that overcomes limitations to traditional rotation-based paradigms. Future studies should use this device to explore the effect of instructions and conditioning on the development of placebo nausea and to assess the efficacy of conditioning-based interventions for clinical use.