Brontë-Stewart H M, Lisberger S G
Department of Physiology, W. M. Keck Foundation Center for Integrative Neuroscience, University of California, San Francisco 94143.
J Neurosci. 1994 Mar;14(3 Pt 1):1290-308. doi: 10.1523/JNEUROSCI.14-03-01290.1994.
We have used electrical stimulation of the vestibular apparatus to reveal parallels between the physiological responses of the vestibular afferents activated at different currents and the properties of the evoked eye movements before and after magnifying spectacles had been used to cause motor learning in the vestibulo-ocular reflex (VOR). Stimulation with the lowest currents caused little or no eye motion, but activated all the afferents with irregular spontaneous discharge, low sensitivities to head velocity, and highly phasic responses during rapid head turns. Stimulation with moderate currents caused substantial eye motion that was weakly affected by motor learning; these currents activated afferents with a wide range of physiological properties, including many that had intermediate discharge regularity, high sensitivity to head velocity, and clear phasic responses during rapid head turns. Stimulation at still higher currents caused still larger eye movements that were strongly altered by motor learning; these currents activated primarily afferents that had regular spontaneous discharge, lower sensitivities to head velocity, and tonic responses during rapid head turns. Stimulation at the highest currents did not cause any further increment in the amplitude of the evoked eye movement, but activated the afferents with the most regular spontaneous discharge and the lowest sensitivities to head velocity. The data imply that the VOR pathways receive substantial vestibular inputs from afferents with a middle range of thresholds for electrical stimulation. These afferents have a wide range of physiological properties, including a large group that shows substantial phasic responses during rapid head turns. The data also suggest that only a subset of these afferents, primarily those with more regular spontaneous discharge, project into the VOR pathways that are modified in association with motor learning.
我们利用对前庭器官的电刺激，来揭示在不同电流下被激活的前庭传入神经的生理反应，与在使用放大眼镜引起前庭眼反射（VOR）中的运动学习之前和之后诱发的眼球运动特性之间的相似之处。用最低电流进行刺激时，几乎不会引起眼球运动或根本不会引起眼球运动，但会激活所有具有不规则自发放电、对头部速度低敏感性以及在快速转头期间具有高度相位反应的传入神经。用中等电流进行刺激时，会引起明显的眼球运动，且受运动学习的影响较弱；这些电流激活了具有广泛生理特性的传入神经，包括许多具有中等放电规律性、对头部速度高敏感性以及在快速转头期间具有明显相位反应的传入神经。用更高电流进行刺激时，会引起更大的眼球运动，且这些运动因运动学习而发生强烈改变；这些电流主要激活了具有规则自发放电、对头部速度较低敏感性以及在快速转头期间具有紧张性反应的传入神经。用最高电流进行刺激时，诱发的眼球运动幅度没有进一步增加，但激活了具有最规则自发放电和对头部速度最低敏感性的传入神经。数据表明，VOR通路从前庭传入神经接收大量前庭输入，这些传入神经具有中等范围的电刺激阈值。这些传入神经具有广泛的生理特性，包括一大组在快速转头期间表现出明显相位反应的神经。数据还表明，这些传入神经中只有一部分，主要是那些具有更规则自发放电的神经，投射到与运动学习相关而被改变的VOR通路中。
