Brainstem mechanisms in vertical eye movement

为了研究Cajal间质核（INC）在垂直眼运动中的作用，对警觉猫进行了单细胞记录。神经元分为4组；垂直爆发-强直神经元（51.5%），强直神经元（12.9%），爆发神经元（3.8%），其余的细胞不属于这三组中的任何一组，但被音调旋转激活（31.8%）。突发性强直性和强直性神经元的放电频率与眼的垂直位置呈线性相关，且半数以上的放电频率投射到前庭核附近，表明眼的垂直位置信号从前庭核传导回前庭核。单眼垂直直肌因腱切除而变弱，弱眼连续覆盖金属补片以防止视力。当将补片切换到正常眼，使弱眼继续观看时，持续进行俯仰旋转，垂直VOR增益在1小时内逐渐显著增加。当把眼罩换到弱视眼，使正常眼重新开始观看时，VOR增益迅速下降到控制值。由于在没有视觉输入的情况下无法观察到这种可逆的增益变化，因此这些变化是自适应变化，以减少视觉-前庭冲突。在这种适应性增益变化过程中，所有被测的垂直爆发-强直神经元和强直神经元的反应幅度与VOR增益的变化同步发生显著变化，提示它们可能将改变后的VOR增益信号发送到前庭核。这些结果表明，将眼球位置信号从前视区发送到前庭核的中枢反馈参与了正常猫和适应猫垂直VOR的神经整合。

In order to study a role of the interstitial nucleus of Cajal (INC) in vertical eye movements, single cell recording was obtained in alert cats. Neurons were classified into 4 groups; vertical burst-tonic (51.5 %), tonic (12.9 %),burst (3.8 %) neurons, and the remaining cells that did not belong to any of these three groups but that were activated by pitch rotations (31.8 %). Discharge frequencies of burst-tonic and tonic neurons were linearly correlated with vertical eye position, and more than a half of them projected near the vestibular nuclei, suggesting that vertical eye position signal is carried back to the vestibular nuclei from the INC.Neuronal activity was examined in the INC region during adaptive gain change of the vertical vestibulo-ocular reflex (VOR). The vertical recti muscles of one eye were weakened by tenectomy, and the weak eye was continuously covered with a metal patch to prevent vision. When the patch was switched to the normal eye so that the weak eye was viewing while pitch rotations were continuously applied, the vertical VOR gain showed a gradual and significant increase within 1 hour. When the patch was switched to the weak eye so that the normal eye started viewing again, the VOR gain quickly decreased to the control values. Since such reversible gain change was not observed without visual input, these changes are adaptive changes to reduce visual-vestibular conflict. During such adaptive gain change, all the vertical burst-tonic and tonic neurons tested showed significant changes in response amplitudes in parallel with the change in the VOR gain, suggesting that they may send the altered VOR gain signal to the vestibular nuclei. These results suggest that the central feedback which sends eye position signal from the INC to the vestibular nuclei is involved in the neural integration of the vertical VOR in normal and adapted cats.