Scheuerer W, Büttner U, Straube A
Neurologische Klinik, Klinikum Grosshadern, Munich, Germany.
Exp Brain Res. 1998 Dec;123(4):361-7. doi: 10.1007/s002210050581.
It is still not clear whether the transition from pursuit eye movements to fixation is mediated by the same system that initiates pursuit, or whether another system, a specialized fixation system, is responsible. To investigate this question we measured smooth-pursuit eye movements and smooth-pursuit termination in five normal subjects using both predictable and unpredictable step-ramp stimuli (velocities 10 degrees and 20 degrees/s) in front of a homogeneous and a structured visual background in order to compare the profile of eye velocity under these different conditions. With the predictable and/or structured visual background there was a gradual transition of eye velocity toward zero. In contrast, with the unpredictable stimulus in front of a homogeneous background, eye velocity during the offset was characterized by an overshoot (on the average, 2.2+/-1.0 degrees/s for 10 degrees/s ramps) before eye velocity settled at zero. Under this condition, steady-state velocity gain and the deceleration of the offset were significantly higher than during the other paradigm with the same target velocity. The latency of the pursuit offset was significantly shorter when a predictable stimulus was used. The duration of the offset did not depend on the experimental condition used. These findings imply that the pursuit onset and offset have some similarities and may be mediated by the same oculomotor system.
从追踪眼动转换为注视究竟是由启动追踪的同一系统介导，还是由另一个系统，即专门的注视系统负责，目前仍不清楚。为了研究这个问题，我们对五名正常受试者进行了测量，在均匀和结构化视觉背景前使用可预测和不可预测的阶跃斜坡刺激（速度为10度/秒和20度/秒）来测量其平稳追踪眼动和平稳追踪终止情况，以便比较在这些不同条件下的眼速度特征。在可预测和/或结构化视觉背景下，眼速度逐渐向零过渡。相比之下，在均匀背景前使用不可预测刺激时，眼速度在偏移期间的特征是在眼速度稳定到零之前出现过冲（对于10度/秒的斜坡，平均为2.2±1.0度/秒）。在这种情况下，稳态速度增益和偏移的减速明显高于相同目标速度下的其他范式。使用可预测刺激时，追踪偏移的潜伏期明显更短。偏移的持续时间不取决于所使用的实验条件。这些发现表明，追踪的起始和终止有一些相似之处，可能由同一动眼系统介导。
