SACCADE-RELATED ACTIVITY IN MONKEY SUPERIOR COLLICULUS .2. SPREAD OF ACTIVITY DURING SACCADES
SACCADE-RELATED ACTIVITY IN MONKEY SUPERIOR COLLICULUS .2. SPREAD OF ACTIVITY DURING SACCADES
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DOI：
10.1152/jn.1995.73.6.2334
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发表时间：
1995-06-01
影响因子：
2.5
通讯作者：
WURTZ, RH
中科院分区：
文献类型：
--
作者：
MUNOZ, DP;WURTZ, RH
1.在另一篇文章中，我们描述了猴上级丘（SC）中与扫视产生有关的两类细胞，即积聚细胞和爆发细胞，它们属于SC中间层的两个功能亚层。积聚细胞与猫中的细胞有几个共同的特征，被描述为具有一个“活动山”在SC上移动，但爆发细胞没有这样的特征。在本文中，我们进一步调查是否有证据表明，这种移动山的活动在猴子通过分析的空间和时间活动的细胞在整个SC在视觉引导扫视的一代。我们记录了猴子进行不同幅度（0.5 - 60度）扫视时单细胞的活动。我们记录了从吻侧到尾侧SC延伸的位置的细胞，以采样其最佳幅度范围从小到大的扫视的细胞。这使我们能够在扫视之前、期间和之后看到SC上的任何活动变化。它也使我们能够确定在眼跳产生的连续阶段中活跃的SC的分数。在主动视注视过程中，前极的注视细胞放电频率增加。从群体重建，我们估计，在每个SC的最嘴0.72毫米的活动细胞区跨越。假设SC是5毫米的长度，类似于15%的细胞躺在沿着水平子午线在建设层将是活跃的在固定期间。至少100毫秒前开始的扫视，长导联活动开始出现在积累层的网站上的SC电机地图相关的下一个扫视。同时，吻极的固定活动开始减弱，而爆发层的细胞保持相对沉默.在扫视开始前约25 ms，固定细胞停止放电，爆发细胞和积聚细胞开始爆发。爆裂层中的活动区估计直径约为1.4 mm，沿从喙极穿过初始活动区中心的直线，约占SC的沿着28%。爆发细胞之间的活动区的大小是独立的扫视幅度。初始活跃区的大小在积聚层中大于在爆发层中，并且取决于扫视幅度;对于较大的扫视，初始活跃区的大小较大。在眼跳过程中，所有的细胞在堆积层躺吻最初的活动区变得活跃，和他们的峰值放电发生后，在眼跳的细胞位于更吻。位于最初活跃的积聚细胞尾部的细胞未被激活。在扫视过程中，在爆裂细胞层的活动崩溃，但有没有在SC中的这种活动的轨迹转移。我们将扫视过程中累积细胞的顺序激活解释为活动在SC累积层的嘴侧扩散。我们没有看到爆发层活动扩散的证据。这些实验使我们能够提出以下序列的活动之间的SC细胞在产生扫视。在固定过程中，活动仅限于固定细胞在吻侧SC，我们假设，这些细胞抑制扫视通过抑制连接直接到扫视细胞在尾侧SC和兴奋性连接到全间歇神经元的笔。建立细胞表现出最早的活动之前扫视，我们认为，这种活动是有关的准备，使扫视，包括选择的目标幅度和方向。爆发细胞在扫视开始之前是活跃的，并且可以向笔提供关于扫视的幅度和方向的输入。注视细胞活动的暂停对于眼跳的时机至关重要。我们认为，在建设细胞的活动，并在突发细胞放电的急剧减少，是一致的反馈信号的SC从笔的吻传播。我们的结论是，这些变化的时空分布在猴子SC的活动是至关重要的控制时，扫视发生，其幅度和方向，以及其轨迹。
1. In the companion paper we described two classes of cells in the monkey superior colliculus (SC) that were related to saccade generation, buildup cells and burst cells, which fell into two functional sublayers within the intermediate layers of the SC. Fixation cells in the rostral SC were deemed to be part of the buildup cell layer. The buildup cells had several characteristics in common with cells in the cat described as having a ''hill of activity'' moving across the SC, but the burst cells had no such characteristics. In this paper we further investigate whether there is evidence for such a moving hill of activity in the monkey by analyzing the spatial and temporal activity of cells across the SC during the generation of visually guided saccades.2. We recorded the activity of single cells while the monkey made saccades of different amplitudes (0.5-60 degrees). We recorded cells from locations extending from the rostral to caudal SC in order to sample cells whose optimal amplitudes ranged from small to large saccades. This allowed us to see any shift of activity across the SC before, during, and after saccades. It also allowed us to determine the fraction of the SC that was active during the successive phases of saccade generation.3. During active visual fixation, the fixation cells in the rostral pole of the buildup layer showed an increased discharge rate. From the population reconstruction, we estimate that the zone of active cells spanned the most rostral 0.72 mm in each SC. Assuming the SC is 5 mm in length, similar to 15% of the cells lying along the horizontal meridian in the buildup layer would be active during fixation.4. At least 100 ms before the initiation of a saccade, long-lead activity began to appear in the buildup layer at the site on the SC motor map related to the next saccade. Fixation activity in the rostral poles simultaneously began to diminish, but the cells in the burst layer remained relatively silent.5. Approximately 25 ms before saccade onset, the fixation cells ceased firing and both burst and buildup cells began to burst. The active zone in the burst layer was estimated to be similar to 1.4 mm diam, occupying roughly 28% of the SC along a line sunning from the rostral pole through the center of the initially active zone. The size of this active area among the burst cells was independent of saccade amplitude. The size of the initially active zone in the buildup layer was larger than in the burst layer and was dependent on saccade amplitude; it was larger for larger saccades.6. During the saccade, all cells in the buildup layer lying rostral to the initially active zone became active, and their peak discharge occurred later in the saccade as the cells were located more rostrally. Cells lying caudal to the initially active buildup cells were not activated. During the saccade, activity in the burst cell layer collapsed, but there was no shift in the locus of this activity in the SC.7. We interpret the sequential activation of the buildup cells during a saccade as a spread of activity rostrally across the buildup layer of the SC. We saw no evidence for a spread of activity in the burst layer.8. These experiments allow us to propose the following sequence of activity among the SC cells during generation of a saccade. During fixation, activity is confined to the fixation cells in the rostral SC, and we hypothesize that these cells suppress saccades via inhibitory connections directly onto the saccade cells in the caudal SC and excitatory connections onto the omnipause neurons in the pens. The buildup cells show the earliest activity preceding a saccade, and we suggest that this activity is related to preparation to make a saccade, including selection of target amplitude and direction. The burst cells are active just before saccade onset and could provide input to the pens for the amplitude and direction of the saccade. The pause in activity of the fixation cells is critical for the timing of the saccade. We think that the rostral spread of activity in the buildup cells, and the sharp reduction in burst cell discharge, are consistent with a feedback signal to the SC from the pens. We conclude that these changes in the spatiotemporal distribution of activity in the monkey SC are critical for controlling when a saccade occurs, its amplitude and direction, and its trajectory.