Effects of cosmonaut vestibular training on vestibular function prior to spaceflight

The purpose of this study was to quantify the effects of repetitive Coriolis and cross-coupled stimulations, similar to the vestibular training the cosmonauts are exposed to prior to their spaceflight, on vestibular function in control subjects on Earth. Ten volunteers were passively rotated in yaw on a rotating chair while executing standardized pitch head-and-trunk movements. The chair stopped to change direction after 12 head-and-trunk movements were made. The runs were grouped in sessions of ten,which were repeated daily for 10 days. The severity of motion sickness was assessed by subjective judgment and measurements of skin pallor and salivary total protein concentration, and nystagmus was recorded. The severity of motion sickness and nystagmus decreased during cosmonaut vestibular training (CVT). One month after the end of CVT, nystagmus responses were still about 20-30% lower than control values. These results indicate that CVT induces a habituation of vestibular responses. One important implication of this experiment concerns space studies on cosmonauts who are exposed to such vestibular training prior to their spaceflight.