Influence of visual and vestibular interaction upon the onset of motion sickness

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We investigated the influence between visual and vestibular interaction upon the onset of motion sickness. In this rescarch, we performed two trials, one was the investigation of rotary/floating sensation during optokinetic (OK) stimulation, and the other, that of the influence of visual target during lincar acceleration upon the onset of motion sickness.During optokinetic nystagmus (OKN) testing many test subjects feel rotary sensation. In order to investigate the influence of the stimulating strength to the peripheral retina, two kinds of OKN,one visual target of which was wide visual angle stripes (SOKN), and the other, numerous random dots (ROKN), were tested to 22 healthy subjects. The test subjects were requested to inform the first time when they felt rotatory sensation (TR) by a hand switch. The time until an optokinetic adapatation limit (TOAL) was analyzed by manual measurement on the graph of slow phase velocity time course. There was no difference between the average of TOT … More AL in SOKN and that in ROKN.In SOKN, the average of TR was almost similar to that of TOAL.On the other hand, the average of TR in ROKN was significantly shorter than that in SOKN.In both testing consitions, TR significantly correlated to TOAL.In OKN by a constant acceleration, because the slow phase velocity cannot completely follow the target velocity, retinal slip occurs and increases according to an increase of the target velocity. The increase of the retinal slip might cause optokinetic induced vertigo by the visual and vestibular interaction. In SOKN,our results, that the average of TR was similar to that of TOAL and that TR highly correlated to TOAL,indicate that the retinal slip quickly increases shortly before or after TOAL.On the other hand, in ROKN,although TR highly correlated to TOAL,the average TR was about 14 see shorter than in SOKN.In ROKN,which stimulates the periphcral visual field stronger than in SOKN, the less retinal slip could cause the stronger visual induced vertigo by optokinetic stimulation. Morcover, test subjects complained stronger rotary sensation by the summation of linear acceleration and optokinetic stimulation than by that of rotary movement and optokinetic atimulation. This results indicates that stimulation to the otolithy more strongly affected to the vestibulo-ocular intcraction and to the vestibulo autonomic reflex than to the semicircular canals.Our result seemed to provide useful information to the study about the influence of vision to motion sickness. Less