Psychophysical studies of visuo-vestibular interaction in microgravity

Vertical linear vection from stimulation with a sinus velocity profile was investigated in two cosmonauts during two long term space flights and the results were compared to vertical vection responses of a cosmonaut who had been tested during the first days in microgravity of a previous space flight. While the pursuit ability in the eye/hand sensorimotor task was stable in all subjects, vertical vection frequency as well as phase response was altered only in the short term cosmonaut during the immediate adaptation phase. The vection responses of the two long term cosmonauts, who were tested after 4 weeks, 10 weeks and 14 weeks respectively in microgravity were much more stable. These findings correlate with the suggestion of different phases of adaptation to microgravity at different flight stages.