Lee C, Zee D S, Straumann D
Department of Psychology, Seoul National University, Seoul 151-742, Korea.
J Neurophysiol. 2000 Jun;83(6):3241-53. doi: 10.1152/jn.2000.83.6.3241.
Rapid eye movements include saccades and quick phases of nystagmus and may have components around all three axes of ocular rotation: horizontal, vertical, and torsional. In this study, we recorded horizontal, vertical, and torsional eye movements in normal subjects with their heads upright and stationary. We asked how the eyes are brought back to Listing's plane after they are displaced from it. We found that torsional offsets, induced with a rotating optokinetic disk oriented perpendicular to the subject's straight ahead, were corrected during both horizontal and vertical voluntary saccades. Thus three-dimensional errors are synchronously reduced during saccades. The speed of the torsional correction was much faster than could be accounted for by passive mechanical forces. During vertical saccades, the peak torsional velocity decreased and the time of peak torsional velocity was delayed, as the amplitude of vertical saccades increased. In contrast, there was no consistent reduction of torsional velocity or change in time of peak torsional velocity with an increase in the amplitude of horizontal saccades. These findings suggest that 1) the correction of stimulus-induced torsion is neurally commanded and 2) there is cross-coupling between the torsional and vertical but not between the torsional and horizontal saccade generating systems. This latter dichotomy may reflect the fact that vertical and torsional rapid eye movements are generated by common premotor circuits located in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). When horizontal or vertical saccade duration was relatively short, the torsional offset was not completely corrected during the primary saccade, indicating that although the saccade itself is three-dimensional, saccade duration is determined by the error in the horizontal or the vertical, but not by the error in the torsional component.
快速眼动包括扫视和眼球震颤的快相，可能在眼球旋转的所有三个轴上都有成分：水平轴、垂直轴和扭转轴。在本研究中，我们记录了正常受试者头部直立且静止时的水平、垂直和扭转眼动。我们研究了眼睛从利斯廷平面移位后如何回到该平面。我们发现，当使用垂直于受试者正前方方向旋转的视动盘诱导产生扭转偏移时，在水平和垂直随意扫视过程中扭转偏移都得到了校正。因此，在扫视过程中三维误差会同步减小。扭转校正的速度比被动机械力所能解释的要快得多。在垂直扫视过程中，随着垂直扫视幅度的增加，扭转峰值速度降低，扭转峰值速度出现的时间延迟。相比之下，随着水平扫视幅度的增加，扭转速度并没有持续降低，扭转峰值速度出现的时间也没有变化。这些发现表明：1）刺激诱导的扭转校正是由神经指令控制的；2）扭转扫视生成系统与垂直扫视生成系统之间存在交叉耦合，但与水平扫视生成系统之间不存在交叉耦合。后一种二分法可能反映了这样一个事实，即垂直和扭转快速眼动是由位于内侧纵束吻侧间质核（riMLF）的共同运动前通路产生的。当水平或垂直扫视持续时间相对较短时，在初级扫视过程中扭转偏移并未完全校正，这表明尽管扫视本身是三维的，但扫视持续时间是由水平或垂直方向的误差决定的，而不是由扭转分量的误差决定的。
