Vertical optokinetic nystagmus (OKN) and optokinetic after-nystagmus (OKAN) studied in 4 subjects during parabolic flights were compared with data obtained on 2 subjects before, during, and after a 7-day space shuttle flight. In parabolic flight, the vertical OKAN following upgoing optokinetic stimulation increased during the 0 g phase, and decreased during the 1.8 g phase. In spaceflight, the vertical OKN gain asymmetry showed a reversal during early exposure to microgravity. This asymmetry reversal is likely the same effect seen in parabolic flight and could be a direct response to the change in otolithic output. However, if asymmetry changes were due only to the otolithic sensory input, we would also expect large changes upon return to normal gravity. Instead, there were large OKN and OKAN changes at the beginning of the flight, but the deviation from the original vertical OKN gain asymmetry constantly decreased throughout the flight and continued post-flight until pre-flight asymmetry value was restored. This suggests one adaptive goal which reinstates the original pre-flight gain and asymmetry value regardless of changing inputs. This adaptation resembles mechanisms seen in posture experiments where the motor programs on Earth are reinstated in microgravity after a period of adjustment.
Up-down asymmetry of vertical optokinetic nystagmus and after-nystagmus elicited in microgravity
IAF, International Astronautical Congress ; 1993 ; Graz, Austria
1993-10-01
Conference paper
No indication
English
Interrelation of optokinetic nystagmus response and recognation visual acuity
British Library Conference Proceedings | 2004
|Pseudo-latent nystagmus: congenital nystagmus with exophoria
British Library Conference Proceedings | 1992
|Modulation of optokinetic nystagmus in humans by linear acceleration, and the effects of spaceflight
DSpace@MIT | 1992
|