Neural readaptation to earth's gravity following return from space

The consequence of exposure to microgravity on the otolith organs was studi ed by recording the responses of vestibular nerve afferents supplying the u tricular otolith organ to inertial accelerations in four toadfish, Opsanus tau, sequentially for 5 days following two National Aeronautics and Space A dministration shuttle orbital flights. Within the first day postflight, the magnitude of response to an applied translation was on average three times greater than for controls. The reduced gravitational acceleration in orbit apparently resulted in an upregulation of the sensitivity of utricular aff erents. By 30 h postflight, responses were statistically similar to control . The time course of return to normal afferent sensitivity parallels the re ported decrease in vestibular disorientation in astronauts following return from space.