Crawford J Douglas, Tweed Douglas B, Vilis Tutis
Canadian Institutes for Health Research Group for Action and Perception, York University, Toronto, Ontario M3J 1P3, Canada.
J Neurophysiol. 2003 Oct;90(4):2777-84. doi: 10.1152/jn.00231.2003.
Static head roll about the naso-occipital axis is known to produce an opposite ocular counterroll with a gain of approximately 10%, but the purpose and neural mechanism of this response remain obscure. In theory counterroll could be maintained either by direct tonic vestibular inputs to motoneurons, or by a neurally integrated pulse, as observed in the saccade generator and vestibulo-ocular reflex. When simulated together with ocular drift related to torsional integrator failure, the direct tonic input model predicted that the pattern of drift would shift torsionally as in ordinary counterroll, but the integrated pulse model predicted that the equilibrium position of torsional drift would be unaffected by head roll. This was tested experimentally by measuring ocular counterroll in 2 monkeys after injection of muscimol into the mesencephalic interstitial nucleus of Cajal. Whereas 90 degrees head roll produced a mean ocular counterroll of 8.5 degrees (+/-0.7 degrees SE) in control experiments, the torsional equilibrium position observed during integrator failure failed to counterroll, showing a torsional shift of only 0.3 degrees (+/-0.6 degrees SE). This result contradicted the direct tonic input model, but was consistent with models that implement counterroll by a neurally integrated pulse.
已知绕鼻枕轴的静态头部转动会产生约10%增益的相反眼动反向转动，但这种反应的目的和神经机制仍不清楚。理论上，反向转动可以通过前庭对运动神经元的直接紧张性输入来维持，也可以通过神经整合脉冲来维持，如在扫视发生器和前庭眼反射中观察到的那样。当与与扭转整合器故障相关的眼动漂移一起模拟时，直接紧张性输入模型预测漂移模式会像在普通反向转动中那样发生扭转性移动，但整合脉冲模型预测扭转漂移的平衡位置不会受头部转动影响。通过在2只猴子的中脑 Cajal 间质核注射蝇蕈醇后测量眼动反向转动，对这一情况进行了实验测试。在对照实验中，90度头部转动产生了平均8.5度（±0.7度标准误）的眼动反向转动，而在整合器故障期间观察到的扭转平衡位置未能反向转动，仅显示出0.3度（±0.6度标准误）的扭转移动。这一结果与直接紧张性输入模型相矛盾，但与通过神经整合脉冲实现反向转动的模型一致。
