Effect of water immersion on post-rotatory and caloric nystagmus

Caloric nystagmus and post-rotatory nystagmus were recorded with and without head-out water immersion. As water immersion reduces body weight by about 90% owing to buoyancy, it decreases somatosensory inputs. Thus water immersion can be used to simulate a weightless environment. Caloric nystagmus was enhanced significantly by water immersion; however, post-rotatory nystagmus was not. These findings demonstrate that caloric nystagmus is easily affected by water immersion which decreases somatosensory inputs, but that post-rotatory nystagmus is not.