振子用回転検査を用いた体性感覚入力の影響の検討

抄録

To evaluate the influence of somatosensory input on the vestibulo-ocular reflex (VOR), we assessed 19 young, healthy volunteers with sinusoidal rotation tests. For the control condition, subjects, with their eyes open, were sinusoidally rotated in complete darkness at a frequency of 0.2 Hz with a maximum angular velocity of 30°/s for 30 seconds, and at frequencies of 0.4 and 0.8 Hz with a maximum angular velocity of 60°/s for 30 seconds. Sinusoidal tests were performed at earth vertical axis rotation (EVAR) and 30°nose-up, off-vertical axis rotation (OVAR). In addition to these controls, we implemented two different somatosensory stimulation conditions during the rotation tests as follows. (1) Subjects were told to grasp an earth-fixed metallic bar with their right hand. Thus, their right arm continued to move as the rotating chair apparatus moved. (2) Subjects put a vibrating belt around their waists, so that they felt vibrations on their trunk. We observed a significant increment (34%) in VOR gain change only at 0.2 Hz EVAR when subjects held the bar compared to that of the controls, who did not hold the bar. Gain change did not differ significantly across the other conditions, including OVAR or vibration stimulation. We propose that arthrokinetic input (i.e., arm movement) had an additive effect on VOR in this study. This input might relate to a low-frequency component that strongly enhances the velocity storage system. Our findings have applications to types of vestibular rehabilitation regimens that implement somatosensory input. Space motion sickness remains a troublesome, serious problem for astronauts traveling in space. This condition frequently occurs shortly after attainment of and sustained exposure to microgravity and affects 73% of crewmembers on the first 2 or 3 days of their initial flight. We hypothesized that somatosensory input supports may reduce dizziness or space motion sickness.