脑干追踪通路:在联合眼-头注视追踪过程中分离视觉、前庭和本体感觉输入

Brain stem pursuit pathways: dissociating visual, vestibular, and proprioceptive inputs during combined eye-head gaze tracking.

作者信息

Roy Jefferson E, Cullen Kathleen E

机构信息

Aerospace Medical Research Unit, Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada.

出版信息

J Neurophysiol. 2003 Jul;90(1):271-90. doi: 10.1152/jn.01074.2002.

Abstract

Eye-head (EH) neurons within the medial vestibular nuclei are thought to be the primary input to the extraocular motoneurons during smooth pursuit: they receive direct projections from the cerebellar flocculus/ventral paraflocculus, and in turn, project to the abducens motor nucleus. Here, we recorded from EH neurons during head-restrained smooth pursuit and head-unrestrained combined eye-head pursuit (gaze pursuit). During head-restrained smooth pursuit of sinusoidal and step-ramp target motion, each neuron's response was well described by a simple model that included resting discharge (bias), eye position, and velocity terms. Moreover, eye acceleration, as well as eye position, velocity, and acceleration error (error = target movement - eye movement) signals played no role in shaping neuronal discharges. During head-unrestrained gaze pursuit, EH neuron responses reflected the summation of their head-movement sensitivity during passive whole-body rotation in the dark and gaze-movement sensitivity during smooth pursuit. Indeed, EH neuron responses were well predicted by their head- and gaze-movement sensitivity during these two paradigms across conditions (e.g., combined eye-head gaze pursuit, smooth pursuit, whole-body rotation in the dark, whole-body rotation while viewing a target moving with the head (i.e., cancellation), and passive rotation of the head-on-body). Thus our results imply that vestibular inputs, but not the activation of neck proprioceptors, influence EH neuron responses during head-on-body movements. This latter proposal was confirmed by demonstrating a complete absence of modulation in the same neurons during passive rotation of the monkey's body beneath its neck. Taken together our results show that during gaze pursuit EH neurons carry vestibular- as well as gaze-related information to extraocular motoneurons. We propose that this vestibular-related modulation is offset by inputs from other premotor inputs, and that the responses of vestibuloocular reflex interneurons (i.e., position-vestibular-pause neurons) are consistent with such a proposal.

摘要

内侧前庭核内的眼-头(EH)神经元被认为是平稳跟踪过程中眼外运动神经元的主要输入:它们接收来自小脑绒球/腹侧旁绒球的直接投射,进而投射到展神经运动核。在此,我们在头部固定的平稳跟踪和头部自由的联合眼-头跟踪(注视跟踪)过程中记录了EH神经元的活动。在头部固定的正弦和阶跃斜坡目标运动的平稳跟踪过程中,每个神经元的反应都可以用一个简单的模型很好地描述,该模型包括静息放电(偏差)、眼位和速度项。此外,眼加速度以及眼位、速度和加速度误差(误差=目标运动-眼运动)信号在塑造神经元放电方面不起作用。在头部自由的注视跟踪过程中,EH神经元的反应反映了它们在黑暗中被动全身旋转时的头部运动敏感性和平稳跟踪时的注视运动敏感性的总和。事实上,在这些不同条件下(例如联合眼-头注视跟踪、平稳跟踪、黑暗中的全身旋转、头部移动时观察目标移动时的全身旋转(即抵消)以及头部在身体上的被动旋转)的这两种范式中,EH神经元的反应可以通过它们的头部和注视运动敏感性得到很好的预测。因此,我们的结果表明,前庭输入而非颈部本体感受器的激活会影响头部在身体上运动时EH神经元的反应。通过证明在猴子颈部以下身体的被动旋转过程中,同一神经元完全没有调制,这一观点得到了证实。综合我们的结果表明,在注视跟踪过程中,EH神经元将前庭以及与注视相关的信息传递给眼外运动神经元。我们提出,这种与前庭相关的调制被来自其他运动前输入的信号所抵消,并且前庭眼反射中间神经元(即位置-前庭-暂停神经元)的反应与这一观点一致。

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