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摘要: 眼球在眼眶中位置的准确信息可从视觉反馈、动眼神经指令的输出复制、眼外肌(EOM)的本体感觉信号中获得,对于视觉反馈、动眼神经指令已有很多研究,但是对于EOM本体感觉信号的中央处理机制仍有待阐明,在不接触眼球的情况下诱导被动眼球运动是该研究领域面临的一个挑战。为此,本研究建立了一种崭新的可诱导大鼠眼球被动运动的方法:将一个直径0.7毫米、厚度0.5毫米的小型稀土磁铁盘附着在大鼠眼球表面,在距离磁铁8–15毫米处放置一根电磁(EM)线圈包裹的直径5毫米金属棒。通过EM线圈通电流,产生电磁力(EMF),作用于眼球表面的磁铁,诱导可控的被动眼球运动。该眼球运动方向取决于电流极性,振幅和峰值速度取决于电流强度和持续时间。EMF诱导的眼动峰值速度与振幅呈线性相关,其主序关系与清醒大鼠的扫视,以及微电刺激麻醉大鼠外展神经核诱导的眼动相似。组织学检查显示,重复的EMF刺激未造成EOM肌纤维损伤。这些结果证明EMF可作为一种新的工具,用于研究EOM本体感觉信号在视觉定位以及凝视控制中的作用。Abstract: Accurate information on eye position in the orbit is available from visual feedback, efference copy of the oculomotor commands and proprioceptive signals from the extraocular muscles (EOM). Whereas visual feedback and oculomotor commands have been extensively studied, central processing of EOM proprioceptive signals remains to be elucidated. A challenge to the field is to develop an approach to induce passive eye movements without physically contacting the eyes. A novel method was developed to generate passive eye movements in rats. A small rare-earth magnet disk (0.7 mm diameter, 0.5 mm thickness) was attached to the surface of a rat’s eyeball. A metal rod (5 mm diameter) wrapped with an electromagnetic (EM) coil was placed near the magnet (8–15 mm). By passing currents to the EM coil, electromagnetic force (EMF) was generated and acted upon the magnet and induced passive eye movements. The EMF induced well-defined passive eye movements, whose directions were dependent on current polarity and amplitudes and peak velocities were dependent on current intensity and duration. Peak velocities of the EMF-induced eye movements were linearly related to amplitudes, exhibiting main sequence relationships similar to that of saccades in awake rats and eye movements induced by electrical microstimulation of the abducens nucleus in anesthetized rats. Histological examination showed that repetitive EMF stimulations did not appear to result in damages in the EOM fibers. These results validated the EMF approach as a novel tool to investigate EOM proprioceptive signals and their roles in visual localization and gaze control.
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Key words:
- Eye movement /
- Proprioception /
- Extraocular muscles
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