Short-latency eye movements evoked by near-threshold galvanic vestibular stimulation
Short-latency eye movements evoked by near-threshold galvanic vestibular stimulation
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DOI：
10.1007/s00221-002-1326-z
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发表时间：
2003-02-01
影响因子：
2
通讯作者：
Bronstein, AM
中科院分区：
文献类型：
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作者：
Cauquil, AS;Faldon, M;Bronstein, AM
为了研究眼和身体对前庭电刺激（GVS）的反应的主要平面是否一致，我们测量了6名正常人受试者双侧双极GVS的双眼三维眼球运动（巩膜线圈技术）。故意将刺激强度保持在较低水平，以表征对接近阈值刺激强度（0.1-0.9 mA）的反应，该刺激强度之前曾用于抑制身体姿势反应。施加刺激4 s，但仅测量在打开或关闭电流的初始300 ms内发生的早期反应。在0.1-0.7 mA的强度下，“开”响应几乎完全由扭转慢相眼运动组成，其中眼睛的顶部朝向阳极旋转。扭体反应潜伏期约为1.5 ± 1.5。还观察到弱的极性依赖性非共轭响应，其中intorting眼升高而extorting眼降低（“斜视眼偏差”）。当电流被切断时，类似的反应发生在相反的方向上。移除视觉固定发光二极管（LED）对短潜伏期眼反应没有一致的影响。眼反应的方向与姿势反应的方向相似，并且与GVS兼容，GVS诱导头部朝向阴极的明显动态侧倾。然而，弱水平眼球运动，这变得更加突出的刺激强度增加到0.9毫安，也被观察到。这表明在GVS诱发的信号中包含关于偏航轴的附加弱旋转分量或额状面中的侧向平移分量。眼球运动的整体模式表明，半规管传入有助于这些低强度的GVS反应。
To investigate whether the primary planes of eye and body responses to galvanic vestibular stimulation (GVS) are congruent, we have measured the binocular, three-dimensional eye movements (scleral coil technique) to bilateral bipolar GVS in six normal human subjects. Stimulation intensities were kept deliberately low in order to characterize the response to near-threshold intensities of stimulation (0.1-0.9 mA) that had been used previously to characterise body postural responses. Stimuli were applied for 4 s, but only the early responses that occurred within the initial 300 ms of turning the current on or off were measured. At intensities of 0.1-0.7 mA the 'on' response consisted almost exclusively of a torsional slow phase eye movement in which the top of the eyes rotated towards the anode. The latency of the torsional response was ca. 46 ms. A weak polarity-dependent disconjugate response was also observed in which the intorting eye elevated and the extorting eye depressed ('skew eye deviation'). When the current was turned off similar responses occurred in the reverse direction. Removal of the visual fixation light-emitting diode (LED) had no consistent effect on the short-latency ocular responses. The direction of the ocular response was similar to that of the postural response and is compatible with GVS inducing an apparent dynamic roll-tilt of the head towards the cathode. However, weak horizontal eye movements, which became more prominent as the stimulus intensity was increased to 0.9 mA, were also observed. This suggests that an additional weak rotational component about the yaw axis, or a component of lateral translation in the frontal plane, is contained in the GVS-evoked signal. The overall pattern of eye movement suggests that semicircular canal afferents contribute to these low-intensity GVS responses.