Nagao S, Kitazawa H
Department of Physiology, Jichi Medical School, Yakushiji 3311-1, Minamikawachi, Kawachi, Tochigi 329-0498, Japan.
Neuroscience. 2003;118(2):563-70. doi: 10.1016/s0306-4522(02)00991-0.
There are two different proposals regarding the role of the cerebellar flocculus in the adaptation of the vestibulo-ocular reflex: that the flocculus is the site for both the induction and retention of the adaptation, or that the flocculus plays an important role in the induction, but the vestibular nuclei to which the flocculus issues its efferents are the site of retention. To locate the memory trace for the adaptation of the vestibulo-ocular reflex, we determined effects of acute pharmacological shutdown of the bilateral cerebellar flocculi in four Macaca fuscata. The gain of the horizontal vestibulo-ocular reflex was measured by sinusoidal oscillation of the turntable by 10 degrees (peak-to-peak) at 0.33 Hz in the dark. Two hours of 0.33 Hz-10 degrees sinusoidal oscillation of the turntable while viewing the stationary checked-pattern screen through a x2.2 magnifying lens adaptively increased the horizontal vestibulo-ocular reflex gain by 0.2 on the average. The gain increase lasted for 1 h when the monkeys were left with their heads fixed in darkness, but it disappeared within 24 h after the monkeys were returned to their cages where they had free movements. The effects of injections of 5 or 10% lidocaine chloride into the bilateral floccular areas (8 microl for each side) immediately after adaptation occurred were determined in nine sessions. The gain of the horizontal vestibulo-ocular reflex immediately decreased to the level before the adaptation. These effects of lidocaine lasted for at least 1 h. On the contrary, injections of the same amount of Ringer's solution, tested in eight sessions, hardly affected gain of the horizontal vestibulo-ocular reflex over 1-h period. These depressant effects of lidocaine injections were specific to the gains increased by adaptation. These results suggest that the memory trace for the short-term adaptation of the horizontal vestibulo-ocular reflex gain induced by 2 h of sustained visual-vestibular interactions resides within the flocculus.
关于小脑绒球在前庭眼反射适应过程中的作用，存在两种不同的观点：一种观点认为绒球是适应诱导和维持的部位；另一种观点认为绒球在诱导过程中起重要作用，但绒球发出传出纤维的前庭核是维持的部位。为了定位前庭眼反射适应的记忆痕迹，我们在4只食蟹猴中确定了双侧小脑绒球急性药理学阻断的影响。在黑暗中，通过以0.33Hz的频率将转台进行10度（峰峰值）的正弦振荡来测量水平前庭眼反射的增益。在通过2.2倍放大镜观看静止的方格图案屏幕时，对转台进行2小时的0.33Hz - 10度正弦振荡，水平前庭眼反射增益平均适应性增加0.2。当猴子头部固定在黑暗中时，增益增加持续1小时，但在猴子回到可以自由活动的笼子后24小时内消失。在适应发生后立即向双侧绒球区域注射5%或10%的氯化利多卡因（每侧8微升），在9次实验中确定了其影响。水平前庭眼反射增益立即降至适应前的水平。利多卡因的这些作用持续至少1小时。相反，在8次实验中测试的等量林格氏液注射，在1小时内几乎不影响水平前庭眼反射增益。利多卡因注射的这些抑制作用对适应增加的增益具有特异性。这些结果表明，由2小时持续视觉 - 前庭相互作用诱导的水平前庭眼反射增益的短期适应的记忆痕迹存在于绒球内。
