Spatial orientation of caloric nystagmus in semicircular canal-plugged monkeys
Spatial orientation of caloric nystagmus in semicircular canal-plugged monkeys
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DOI：
10.1152/jn.2002.88.2.914
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发表时间：
2002-08-01
影响因子：
2.5
通讯作者：
Raphan, T
中科院分区：
文献类型：
--
作者：
Arai, Y;Yakushin, SB;Raphan, T
我们研究了堵塞所有六个半规管之前和之后的热量眼球震颤，以确定速度存储是否有助于热量眼球震颤的空间方向。猴子在直立、仰卧、俯卧、右侧朝下和左侧朝下时用冷水（约20℃）进行单侧刺激。慢相速度矢量的下降是在眼球震颤的最后 37% 期间确定的，此时响应主要是由于速度存储的激活。在堵塞之前，偏航分量随所有头部方向的侧管内淋巴对流流动而变化。堵塞阻塞了内淋巴流动，消除了对流。尽管如此，热量眼球震颤很容易引起，但水平分量始终朝向受刺激的（同侧）侧，无论头部相对于重力的位置如何。当直立时，慢相速度矢量接近偏航轴和空间垂直轴。侧倾成分在仰卧位和俯卧位时变得更强，垂直成分在侧卧位时增强。在每种情况下，这都会使速度矢量与空间垂直方向对齐。与控制速度存储方向的原理一致，当速度矢量的偏航分量为正时，交叉耦合的俯仰或滚动分量使矢量在空间中向上。相反，当偏航眼速度矢量在头部坐标系中向下（即负）时，俯仰和滚动在空间中向下。该数据不能简单地通过同侧前庭神经活动的减少来建模，这将沿着滚动方向引导速度矢量。由于从滚转到偏航不存在交叉耦合，因此单独的速度存储无法旋转矢量以适应数据。因此，我们推测，冷却导致了堵塞的耳道中的内淋巴收缩。这种收缩将使壶腹偏向塞子，模拟内淋巴的壶腹流动。这种杯托偏转引起的抑制和兴奋在直立位置时很好地拟合了数据，但在侧向或俯卧/仰卧条件下则不然。数据适合这些位置需要添加空间定向的速度存储组件。因此，我们得出结论，三个因素在管堵塞后产生冷热眼球震颤：壶腹神经活动的抑制，受刺激的管内淋巴的收缩，以及通过速度存储使眼球速度向重力定向。尽管对对流的反应主导了对热量刺激的正常反应，但速度存储可能也有助于眼睛速度的定向。
We studied caloric nystagmus before and after plugging all six semicircular canals to determine whether velocity storage contributed to the spatial orientation of caloric nystagmus. Monkeys were stimulated unilaterally with cold (approximate to20degreesC) water while upright, supine, prone, right-side down, and left-side down. The decline in the slow phase velocity vector was determined over the last 37% of the nystagmus, at a time when the response was largely due to activation of velocity storage. Before plugging, yaw components varied with the convective flow of endolymph in the lateral canals in all head orientations. Plugging blocked endolymph flow, eliminating convection currents. Despite this, caloric nystagmus was readily elicited, but the horizontal component was always toward the stimulated (ipsilateral) side, regardless of head position relative to gravity. When upright, the slow phase velocity vector was close to the yaw and spatial vertical axes. Roll components became stronger in supine and prone positions, and vertical components were enhanced in side down positions. In each case, this brought the velocity vectors toward alignment with the spatial vertical. Consistent with principles governing the orientation of velocity storage, when the yaw component of the velocity vector was positive, the cross-coupled pitch or roll components brought the vector upward in space. Conversely, when yaw eye velocity vector was downward in the head coordinate frame, i.e., negative, pitch and roll were downward in space. The data could not be modeled simply by a reduction in activity in the ipsilateral vestibular nerve, which would direct the velocity vector along the roll direction. Since there is no cross coupling from roll to yaw, velocity storage alone could not rotate the vector to fit the data. We postulated, therefore, that cooling had caused contraction of the endolymph in the plugged canals. This contraction would deflect the cupula toward the plug, simulating ampullofugal flow of endolymph. Inhibition and excitation induced by such cupula deflection fit the data well in the upright position but not in lateral or prone/supine conditions. Data fits in these positions required the addition of a spatially orientated, velocity storage component. We conclude, therefore, that three factors produce cold caloric nystagmus after canal plugging: inhibition of activity in ampullary nerves, contraction of endolymph in the stimulated canals, and orientation of eye velocity to gravity through velocity storage. Although the response to convection currents dominates the normal response to caloric stimulation, velocity storage probably also contributes to the orientation of eye velocity.