<Outline of Experiment>
The purposes of this research are to study the effects of microgravity on the response dynamics of the afferents of the otolithe organs and to study any activation and action of the efferent vestibular system related to the microgravity environment.
The otolith organs in the inner ear sense linear acceleration of the head and function as a gravity sensor. Neural signals from the otolith organs play essential roles in maintaining balance and posture. This function is known to be common for all species from fish to higher mammals. The responses of otolithic afferents in microgravity may be quite different from that on the ground, and this difference may disturb the brain. This is considered to be one of the causes for space motion sickness. But if the period of stay in space becomes long, it is hypothesized that the efferent system which modifies the afferent signals would work so as to restore the otolithic function.
An aquatic animal, the toadfish, will be used for this experiment. The activity of otolithic afferents will be chronically monitored using specially designed electrodes to characterize their responses in normal and microgravity. The effects of reduced gravity upon the preformance of the otolithic organs and the action of the efferent system will be analyzed in detail.

<Expected results>
Results of the experiment will add information about the etiologies of space adaptation syndrome and may bear upon future therapies and mechanisms for the control of equilibrium disfunctions such as earth bound motion sickness.

Semi-circular canals and otolith Structure of otolith organs

Last Updated : March 27, 1998