Castellote Juan M, Kumru Hatice, Queralt Ana, Valls-Solé Josep
Facultad de Ciencias de la Actividad Física y el Deporte, Universidad de Valencia, 46010, Valencia, Spain.
Exp Brain Res. 2007 Feb;177(1):129-36. doi: 10.1007/s00221-006-0659-4. Epub 2006 Aug 31.
The control of eye movements depends in part on subcortical motor centres. Gaze is often directed towards salient visual stimuli of our environment with no conscious voluntary commands. To further understand to what extent preprogrammed eye movements can be triggered subcortically, we carried out a study in normal volunteers to examine the effects of a startling auditory stimulus (SAS) on externally guided saccades. A peripheral visual cue was presented in the horizontal plane at a site distant 15 degrees from the fixation point, and subjects were instructed to make a saccade to it. SAS was presented together with the peripheral visual cue in 20% of trials. To force rapid visual fixation at the end of the saccade, targets were loaded with a second cue, a small arrow pointing towards the right or the left (or a neutral sign), not distinguishable with peripheral vision. Subjects were requested to perform a flexion/extension wrist movement, according to the direction of the arrow (or not to move if the second cue was the neutral sign). SAS presented together with the visual target caused a significant shortening of the latency of saccadic movements. The wrist movements performed as a response to the second cue had similar reaction times regardless of whether the trial contained a SAS or not. Our results show that voluntary saccades to peripheral targets are speeded up by activation of the startle circuit, and that this effect does not cause a significant disturbance in the execution of simple in-target cues. These results suggest that subcortical structures play a main role in preparation of externally guided saccades.
眼球运动的控制部分依赖于皮层下运动中枢。在没有有意识的自主指令的情况下，目光常常会被引向我们周围环境中显著的视觉刺激。为了进一步了解预先设定的眼球运动在多大程度上可以在皮层下被触发，我们对正常志愿者进行了一项研究，以检查惊人听觉刺激（SAS）对外界引导扫视的影响。在水平面上，在距注视点15度远的位置呈现一个周边视觉线索，受试者被指示向其进行扫视。在20%的试验中，SAS与周边视觉线索同时呈现。为了在扫视结束时强制快速视觉固定，目标带有第二个线索，一个指向右侧或左侧的小箭头（或一个中性标志），周边视觉无法区分。要求受试者根据箭头的方向进行手腕屈伸运动（如果第二个线索是中性标志则不运动）。与视觉目标同时呈现的SAS导致扫视运动的潜伏期显著缩短。无论试验是否包含SAS，作为对第二个线索的反应而进行的手腕运动具有相似的反应时间。我们的结果表明，对周边目标的自主扫视通过惊吓回路的激活而加速，并且这种效应不会在执行简单的目标内线索时引起显著干扰。这些结果表明，皮层下结构在准备外界引导扫视中起主要作用。
