Kleine J F, Guan Y, Buttner U
Department of Neurology, Ludwig-Maximilian University, 81377 Munich, Germany.
J Neurophysiol. 2003 Nov;90(5):3137-54. doi: 10.1152/jn.00021.2003. Epub 2003 Jul 9.
The cerebellar fastigial oculomotor region (FOR) and the overlying oculomotor vermis (OV) are involved in the control of saccadic eye movements, but nature and function of their saccade-related neuronal signals are not fully understood. There is controversy in at least two major aspects: first, lesion studies in OV/FOR reported eye-position-dependent dysmetria-with FOR lesions, centripetal saccades became more hypermetric than centrifugal saccades-suggesting that the cerebellum may compensate for orbital mechanics. However, single-unit studies failed to reveal corresponding eye-position dependencies in FOR saccade-related discharge patterns. Second, some single-unit studies reported precise correlation between burst and saccade duration in the FOR. However, others stated that FOR bursts were only weakly related to saccade properties. In an attempt to resolve these discrepancies, we recorded single FOR units in monkeys that made horizontal saccades (16 degrees ) from different starting positions. Sampling saccades of one fixed amplitude and application of an objective, computer-based burst-detection-routine allowed us to correlate burst parameters (onset latency, peak latency, peak amplitude, number of spikes, duration) and kinematic properties of individual saccades. FOR bursts were found to start and peak earlier and exhibit higher peak burst amplitudes for faster than for slower saccades of the same amplitude. While these correlations between FOR bursts and saccade properties were statistically significant for a minority of approximately 20-25% of individual units, the same effects were also predominant in the remainder of the neuronal sample and statistically significant on the population level. Neuronal activity was not significantly modulated by eye position itself. However, reflecting differences in saccade velocities but not an actual influence of eye position per se, FOR bursts for centripetal and centrifugal saccades exhibited subtle but systematic differences, which closely paralleled, and hence probably explain, the eye-position dependency of deficits observed after FOR inactivation. Our findings indicate that FOR signals reflect much of the kinematic properties of the saccade. Moreover, they are consistent with the idea that the FOR output is purposefully modified according to these kinematic properties to maintain saccadic accuracy.
小脑顶核动眼区（FOR）及覆盖其上的动眼蚓部（OV）参与扫视眼动的控制，但其与扫视相关的神经元信号的本质和功能尚未完全明确。至少在两个主要方面存在争议：第一，对OV/FOR的损伤研究报告了与眼位相关的辨距不良——在FOR损伤时，向心性扫视比离心性扫视的超射现象更明显——这表明小脑可能会补偿眼眶力学因素。然而，单单位研究未能在FOR与扫视相关的放电模式中揭示相应的眼位依赖性。第二，一些单单位研究报告了FOR中爆发与扫视持续时间之间存在精确的相关性。然而，其他研究则指出FOR爆发与扫视特性之间的关系较弱。为了解决这些差异，我们在进行水平扫视（16度）的猴子中记录了单个FOR单位，这些扫视从不同的起始位置发起。对一个固定幅度的扫视进行采样，并应用基于计算机的客观爆发检测程序，使我们能够将爆发参数（起始潜伏期、峰值潜伏期、峰值幅度、尖峰数量、持续时间）与单个扫视的运动学特性相关联。结果发现，对于相同幅度但速度不同的扫视，FOR爆发开始和达到峰值的时间更早，且峰值爆发幅度更高。虽然FOR爆发与扫视特性之间的这些相关性在约20% - 25%的单个单位中具有统计学意义，但在其余神经元样本中这些效应也很显著，且在群体水平上具有统计学意义。神经元活动并未受到眼位本身的显著调节。然而，反映扫视速度的差异而非眼位本身的实际影响，向心性和离心性扫视的FOR爆发表现出细微但系统的差异，这与FOR失活后观察到的缺陷的眼位依赖性密切平行，因此可能对其做出了解释。我们的研究结果表明，FOR信号反映了扫视的许多运动学特性。此外，它们与以下观点一致，即FOR输出会根据这些运动学特性进行有目的的调整，以维持扫视的准确性。
