垂直视动刺激下视－前庭功能的反应特点

Response Characteristics of Visual-Vestibular Function in Humans During Exposures to Vertical Optokinetic Stimulation

在大视野的垂直视动刺激下，观察了２４名正常人的运动病症状、自身运动感觉－翻转错觉、垂直视动眼震（ＶＯＫＮ）、心电图Ｒ－Ｒ间隔功率谱的反应特点。垂直视动刺激由黑背景上随机分布的大小不等运动着的白色圆点的图象构成，视觉刺激是４种运动速度（３０、４５、６０、８０°／ｓ），两种垂直运动方向（上下）。电眼动图（ＥＯＧ）技术记录人的眼球运动。结果发现，向上方向运动的视动刺激诱发的ＶＯＫＮ平均慢相速度和增益比对向下方向运动的显著增大，两种运动方向的ＶＯＫＮ增益随视动速度增加而减少。４５～８０°／ｓ垂直视动刺激下翻转错觉有方向性不对称。不同的垂直视动速度刺激引起运动病的症状不同，４５°／ｓ时诱发的运动病最大。垂直视动刺激中心率和Ｒ－Ｒ间隔功率谱没有显著变化，而前庭刺激（平行秋千６ｍ，３．９５ｍ／ｓ２）下，引起的心率、Ｒ－Ｒ间隔功率谱Ｃ波显著增加。根据视－前庭相互作用调制理论讨论了ＶＯＫＮ和翻转错觉的不对称性，提出视前庭功能的不对称可能是空间运动病的致病因素的一种。

Motion sickness(MS)symptoms, illusory self- motion sensation orpitch vection ,vertical optokinetic nystagmus(VOKN) ,heart rate and spectra of R-R in-tervals were obtained in 24 healthy subjects(4 females ,20 males)while they were view-ing a large optokinetic screen field moving white random-dots display. The optokineticstimulus with velocities of 30,45,60 ,or 8 0°/s and two directions, upward or down-ward ,of motion were presented.The vestibular stimuli was used in a parallel swing(0.22Hz,3.9m/s2).Eye movements of the subjects sitting upright were measured with theEOG technique. The mean velocities of the slow phases of vertical OKN elicited by up-ward motion were significantly higher than those elicited by downward motion at stimulusvelocities between 3 0 and 80°/s. The decrease of the gain of VOKN as a function of in-creasing stimulus veloities was showed. These rusults suggest that diretional asymmetry inVOKN exists in the slow OKN system. The average magnitudes of pitch vection increasedsignificantly in up-down asymmetry at stimulus velocities of 4 5～80°/s. Different op-tokinetic speeds showed different effects on the symptoms of MS. Incidence of symptomsand average scores of MS symptoms are largest at optokinetic stimulus speed of 4 5°/s.No significant changes of heart rate, power spectra of R-R intervals were found duringexposures to vertical optokinetic stimulation , however ,during the parallel swing simula-tion they were higher than before the stimulation. The causes of upward preponderance ofVOKN and pitch vection during vertical optokinetic stimulation were discussed based onthe visual- vestibular modulation theory. It was suggested that the asymmetry of visual-vestibular function might be one of the primary etiological-factors of space MS.