German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-University, Feodor-Lynen-Str.19, 801377, Munich, Germany.
Department of Neurology, Ludwig-Maximilians-University, 801377, Munich, Germany.
Brain Struct Funct. 2017 Dec;222(9):4163-4185. doi: 10.1007/s00429-017-1461-8. Epub 2017 Jun 23.
Optokinetic eye movements are crucial for keeping a stable image on the retina during movements of the head. These eye movements can be differentiated into a cortically generated response (optokinetic look nystagmus) and the highly reflexive optokinetic stare nystagmus, which is controlled by circuits in the brainstem and cerebellum. The contributions of these infratentorial networks and their functional connectivity with the cortical eye fields are still poorly understood in humans. To map ocular motor centres in the cerebellum and brainstem, we studied stare nystagmus using small-field optokinetic stimuli in the horizontal and vertical directions in 22 healthy subjects. We were able to differentiate ocular motor areas of the pontine brainstem and midbrain in vivo for the first time. Direction and velocity-dependent activations were found in the pontine brainstem (nucleus reticularis, tegmenti pontis, and paramedian pontine reticular formation), the uvula, flocculus, and cerebellar tonsils. The ocular motor vermis, on the other hand, responded to constant and accelerating velocity stimulation. Moreover, deactivation patterns depict a governing role for the cerebellar tonsils in ocular motor control. Functional connectivity results of these hubs reveal the close integration of cortico-cerebellar ocular motor and vestibular networks in humans. Adding to the cortical concept of a right-hemispheric predominance for visual-spatial processing, we found a complementary left-sided cerebellar dominance for our ocular motor task. A deeper understanding of the role of the cerebellum and especially the cerebellar tonsils for eye movement control in a clinical context seems vitally important and is now feasible with functional neuroimaging.
视动眼动是头部运动时保持视网膜上稳定图像的关键。这些眼动可以分为皮质产生的反应（视动性眼球震颤）和高度反射性的视动性凝视性眼球震颤，后者由脑干和小脑的回路控制。这些颅后网络的贡献及其与皮质眼区的功能连接在人类中仍知之甚少。为了绘制小脑和脑干中的眼球运动中枢，我们在 22 名健康受试者中使用水平和垂直小视野视动刺激研究了凝视性眼球震颤。我们首次能够在体内区分脑桥和中脑的眼球运动区。在脑桥（网状核、脑桥被盖和旁正中脑桥网状结构）、小舌、绒球和小脑扁桃体中发现了与方向和速度相关的激活。另一方面，眼球运动蚓部对恒速和加速速度刺激有反应。此外，失活模式描绘了小脑扁桃体在眼球运动控制中的主导作用。这些中枢的功能连接结果揭示了人类皮质眼球运动和前庭网络的紧密整合。除了大脑右半球在视觉空间处理中占主导地位的皮质概念外，我们还发现了对我们的眼球运动任务的左小脑优势的补充。深入了解小脑，特别是小脑扁桃体在眼球运动控制中的作用在临床环境中似乎至关重要，并且现在可以通过功能神经影像学来实现。
