Waitzman David M, Pathmanathan Jay, Presnell Rachel, Ayers Amanda, DePalma Stacy
Department of Neurology, University of Connecticut Health Center, Farmington, Connecticut 06030-3974, USA.
Ann N Y Acad Sci. 2002 Apr;956:111-29. doi: 10.1111/j.1749-6632.2002.tb02813.x.
Converging lines of evidence support a role for the intermediate and deep layers of the superior colliculus (SC) and the mesencephalic reticular formation (MRF) in the control of combined head and eye movements (i.e., gaze). Recent microstimulation, single-cell recording, and lesion experiments are reviewed in which monkeys are free to move their heads. Cells in the SC discharge in advance of combined head and eye movements and most likely provide a gaze error signal to downstream structures. In contrast, the neurons in the MRF are of at least two types. Eye cells have features that are similar to neurons in the rostral portion of the SC, but fire before the onset of horizontal eye movments. A second group of MRF neurons begin to fire after the onset of the gaze shift and are most closely associated with movements of the head. The peak discharge of these late-onset MRF neurons occurs near the peak head velocity. Stimulation in the rostral SC generates eye movements with fixed amplitude and direction. A similar response is noted after stimulation of the more dorsal portion of the caudal MRF. Stimulation in the caudal portion of the SC produces combined head and eye movements of fixed amplitude. Electrical activation of the more ventral portions of the caudal MRF generates goal-directed and centering eye movements. Temporary inactivation of the SC with the GABA agonist muscimol generated hypometria and curved trajectories of contralateral eye movements. Inactivation of the caudal MRF produced contralateral hypermetria and ipsilateral hypometria of saccades. Release of the monkey's head demonstrated a profound contralateral head tilt. Taken together, these data suggest that the gaze signal generated in the SC is filtered by neurons in the MRF to generate a feedback signal of eye motor error. The head signal found in the MRF could cancel a portion of the gaze signal coming from the SC in the form of head velocity feedback.
越来越多的证据支持上丘（SC）的中层和深层以及中脑网状结构（MRF）在控制头部和眼睛联合运动（即注视）中发挥作用。本文回顾了近期的微刺激、单细胞记录和损伤实验，实验中猴子可自由移动头部。SC中的细胞在头部和眼睛联合运动之前放电，很可能向下游结构提供注视误差信号。相比之下，MRF中的神经元至少有两种类型。眼细胞具有与SC前部神经元相似的特征，但在水平眼动开始之前放电。第二组MRF神经元在注视转移开始后开始放电，并且与头部运动关系最为密切。这些迟发性MRF神经元的放电峰值出现在头部速度峰值附近。刺激SC前部会产生固定幅度和方向的眼动。刺激尾侧MRF更靠背侧部分后也会出现类似反应。刺激SC尾侧部分会产生固定幅度的头部和眼睛联合运动。电激活尾侧MRF更靠腹侧部分会产生目标导向和定心眼动。用GABA激动剂蝇蕈醇暂时使SC失活会导致对侧眼动幅度减小和轨迹弯曲。尾侧MRF失活会导致扫视时对侧眼动幅度增大和同侧眼动幅度减小。放开猴子的头部会出现明显的对侧头部倾斜。综上所述，这些数据表明，SC中产生的注视信号被MRF中的神经元过滤，以产生眼动误差的反馈信号。MRF中发现的头部信号可以以头部速度反馈的形式抵消一部分来自SC的注视信号。
