Competition between saccade goals in the superior colliculus produces saccade curvature
Competition between saccade goals in the superior colliculus produces saccade curvature
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DOI：
10.1152/jn.00657.2002
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发表时间：
2003-05-01
影响因子：
2.5
通讯作者：
Keller, EL
中科院分区：
文献类型：
--
作者：
McPeek, RM;Han, JH;Keller, EL
当在需要从分心物中选择目标的搜索任务中进行眼跳运动时，这些运动的轨迹比对单一刺激进行的类似眼跳运动显示出更大的曲率。为了验证这种曲率的增加是由运动开始时间附近发生的眼跳目标之间的竞争性相互作用引起的假设，我们在上丘(SC)进行了单单位记录和微刺激实验。我们发现，在目标附近结束但向分心物弯曲的眼跳伴随着编码分心物位置的SC神经元增强的扫视前活动。这种增加的活动发生在眼跳开始前30毫秒，并在眼跳开始时突然消失。牵张器部位活动增加的幅度与牵张器的曲率大小相关。相比之下，编码目标位置的神经元在弯曲眼跳和直眼跳时的放电没有任何显著差异。为了确定这种SC放电模式是否与眼跳曲率有因果关系，我们使用电微刺激进行了第二系列实验。猴子对没有分心的单一视觉刺激进行扫视，我们刺激SC中与搜索任务中分心的地点相对应的地点。这种刺激是诱发眼跳的亚阈值，但当它的时间结构模仿搜索中记录的曲线眼跳活动时，随后对视觉目标的眼跳显示出朝向刺激位置编码的弯曲。刺激频率越高、刺激部位与视觉靶点位于同一丘时，这种影响越大。这些结果支持这样一种假设，即在搜索中观察到的眼跳曲率的增加源于目标和分心目标之间的竞争，并与SC参与眼跳目标选择的竞争性神经相互作用的观点一致。
When saccadic eye movements are made in a search task that requires selecting a target from distractors, the movements show greater curvature in their trajectories than similar saccades made to single stimuli. To test the hypothesis that this increase in curvature arises from competitive interactions between saccade goals occurring near the time of movement onset, we performed single-unit recording and microstimulation experiments in the superior colliculus (SC). We found that saccades that ended near the target but curved toward a distractor were accompanied by increased presaccadic activity of SC neurons coding the distractor site. This increased activity occurred similar to30 ms before saccade onset and was abruptly quenched on saccade initiation. The magnitude of increased activity at the distractor site was correlated with the amount of curvature toward the distractor. In contrast, neurons coding the target location did not show any significant difference in discharge for curved versus straight saccades. To determine whether this pattern of SC discharge is causally related to saccade curvature, we performed a second series of experiments using electrical microstimulation. Monkeys made saccades to single visual stimuli presented without distractors, and we stimulated sites in the SC that would have corresponded to distractor sites in the search task. The stimulation was subthreshold for evoking saccades, but when its temporal structure mimicked the activity recorded for curved saccades in search, the subsequent saccades to the visual target showed curvature toward the location coded by the stimulation site. The effect was larger for higher stimulation frequencies and when the stimulation site was in the same colliculus as the representation of the visual target. These results support the hypothesis that the increased saccade curvature observed in search arises from rivalry between target and distractor goals and are consistent with the idea that the SC is involved in the competitive neural interactions underlying saccade target selection.