Disruption of postural readaptation by inertial stimuli following space flight.

Postural instability (relative to pre-flight) has been observed in all shuttle astronauts studied upon return from orbital missions. Postural stability was more closely examined in four shuttle astronaut subjects before and after an 8 day orbital mission. Results of the pre- and post-flight postural stability studies were compared with a larger (n = 34) study of astronauts returning from shuttle missions of similar duration.

Motion sickness and development of synergy within the spatial orientation system. A hypothetical unifying concept.

Adaptation to research paradigms such as rotating rooms and optical alteration of visual feedback during movement results in development of perceptual-motor programs that provide the reflexive assistance that is necessary to skilled control of movement and balance. The discomfort and stomach awareness that occur during the adaptation process has been attributed to conflicting sensory information about the state of motion. Vestibular signals depend on the kinematics of head movements irrespective of the presence or absence of signals from other senses.

Microgravity vestibular investigations: perception of self-orientation and self-motion.

Four astronauts experienced passive whole-body rotation in a number of test sessions during a 7-day orbital mission. Pitch (Y-axis) and roll (X-axis) rotation required subject orientations on the rotator in which the otolith system was at radius of 0.5 m.

Vertical optokinetic nystagmus and after-responses during backward tilt.

Method: Vertical optokinetic nystagmus (VOKN) and after-responses were detected in nine subjects using the corneo-retinal potential (CRP) technique and an infrared video camera detection apparatus (ISCAN) simultaneously. The ISCAN method produced a much smaller inter-subject variability, a higher linear regression coefficient (0.94) when vertical eye position was regressed against vertical target position (+/- 30 degrees, 5 degrees increments).

Spatial orientation perception and reflexive eye movements--a perspective, an overview, and some clinical implications.

When head motion includes a linear velocity component, eye velocity required to track an earth-fixed target depends upon: a) angular and linear head velocity, b) target distance, and c) direction of gaze relative to the motion trajectory. Recent research indicates that eye movements (LVOR), presumably otolith-mediated, partially compensate for linear velocity in small head excursions on small devices. Canal-mediated eye velocity (AVOR), otolith-mediated eye velocity (LVOR), and Ocular Torsion (OT) can be measured, one by one, on small devices.