Journal of Applied Physiology, Vol 81, Issue 1 69-81, Copyright © 1996 by American Physiological Society
Horizontal angular VOR changes in orbital and parabolic flight: human neurovestibular studies on SLS-2
C. M. Oman, C. F. Pouliot and A. Natapoff
Man-Vehicle Laboratory, Massachusetts Institute of Technology, Cambridge 02139, USA.
Further evidence was found for adaptive changes in the vestibular "velocity
storage" (VS) component of the vestibuloocular reflex in four shuttle
astronauts tested in parabolic flight and before, during, and after a
14-day mission. Nystagmus was recorded during and after 1 min of 120
degrees/s rotation. Gains and time constants were determined by computer
analysis. Responses correlated with experience. Two subjects were making
their first spaceflight. In parabolic flight, their time constants
shortened to an average of 60% of 1 G values, presumably because unfamiliar
otolith cues reduced VS. However, after 4-10 days in orbit, their time
constants were similar or greater than those preflight, indicating VS
recovery. The other two subjects had previously flown in space. Their time
constants shortened in orbit to an average of 69% of 1 G values, indicating
a persisting reduction of VS. This correlation with spaceflight experience
has been seen in 9 of 11 subjects on 3 missions. Head pitch did not
significantly "dump" nystagmus as it does on Earth.
