Combined eye-head gaze shifts produced by electrical stimulation of the superior colliculus in rhesus monkeys
Combined eye-head gaze shifts produced by electrical stimulation of the superior colliculus in rhesus monkeys
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DOI：
10.1152/jn.1996.76.2.927
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发表时间：
1996-08-01
影响因子：
2.5
通讯作者：
Sparks, DL
中科院分区：
文献类型：
--
作者：
Freedman, EG;Stanford, TR;Sparks, DL
1. 我们电刺激了两只恒河猴的上丘（SC）的中层和深层，使它们可以自由地垂直和水平移动头部（头部不受限制）。对灵长类SC的刺激可以引起高速的、联合的、眼-头注视的转移，这种转移类似于视觉引导的注视的幅度和方向。眼球刺激产生的注视位移的幅度取决于刺激的部位和刺激的参数（频率、电流和刺激序列的持续时间）。电刺激在两只恒河猴的上丘脑的56个部位产生了最大幅度的目光转移，其幅度从类似于7度到类似于80度不等。由于头部不受约束，刺激引起的目光转移通常包括头部的运动。在56个刺激点产生的头部运动幅度从0到接近70度3。刺激引起的头部运动和凝视转移的峰值速度和振幅、持续时间和振幅之间的关系与视觉引导下的凝视转移之间的关系相当。眼睛和头部对视觉引导和刺激诱导的凝视转移的相对贡献也相似。与视觉引导的凝视转移一样，头部对刺激引起的凝视转移的贡献取决于刺激开始时眼睛相对于头部的位置。当眼睛偏离随后的注视转移方向时，头部贡献增加，头部运动开始的潜伏期减少。我们系统地改变了刺激序列的持续时间（10-400 ms），而刺激频率和电流保持不变。刺激持续时间的增加系统地增加了引起的凝视转移的幅度，直到达到特定部位的最大幅度。刺激持续时间的进一步增加并没有增加凝视幅度。对于小于特定部位最大振幅的运动，刺激训练的结束与引起的凝视转移的结束之间存在高度的相关性。不同于刺激持续时间对凝视振幅的影响；在测试的持续时间范围内（10-400 ms），诱发的头部运动的幅度和持续时间没有达到饱和，而是随着刺激持续时间的增加而继续线性增加。系统地改变刺激频率（范围：63-1,000 Hz），而其他刺激参数保持不变。引起的注视转移速度与刺激频率有关；更高的增产频率导致更高的峰值速度。最大的部位特异性振幅与刺激频率无关。当使用相同的刺激参数刺激单个collcolli部位时，从不同初始位置开始的刺激引起的凝视位移的幅度和方向相对恒定。相反，这些固定矢量凝视位移的眼睛分量的振幅和方向取决于眼睛在轨道上的初始位置；眼球运动的终点聚集在一个眼窝区域，或称“目标”，这取决于睫体刺激的位置。当使用相同的刺激参数时，当眼睛最初以眼眶为中心时，头部受约束时尾侧丘刺激产生的凝视位移通常小于头部不受约束时同一部位引起的凝视位移。这种衰减发生的原因是，当头部受到约束或不受约束时，刺激将眼睛驱动到大约相同的眼眶位置。因此，当头部受到约束时所产生的运动的幅度减少了，其幅度大约相当于头部在自由运动时所产生的幅度。当头部受到限制时，只观察到预期的目光转移的眼睛部分。这导致了“期望的”凝视振幅与观察到的运动轨迹的分离。因为，在头部受限的刺激过程中，观察到的运动只是由脑丘活动轨迹编码的运动的一部分，所以在头部受限的受试者中使用微刺激定义的脑丘“运动图”可能会被扭曲。从不同的初始位置引起的刺激诱发运动的眼睛、头部和凝视成分的方向不同。例如，在水平子午线以上45度的斜视移动中，目光移动的眼睛部分几乎完全垂直，而头部部分几乎完全水平。这就产生了眼睛、头部和凝视运动方向的分离。总的来说，这些数据与SC产生单独的眼睛和头部位移命令的假设不一致。相反，这些发现被解释为支持这样一种假设，即期望的凝视位移的信号来自于collcollus活动的轨迹。视丘的活动水平可以在不影响移视信号的情况下影响注视移动的速度。
1. We electrically stimulated the intermediate and deep layers of the superior colliculus (SC) in two rhesus macaques free to move their heads both vertically and horizontally (head unrestrained). Stimulation of the primate SC can elicit high-velocity, combined, eye-head gaze shifts that are similar to visually guided gaze shifts of comparable amplitude and direction. The amplitude of gaze shifts produced by collicular stimulation depends on the site of stimulation and on the parameters of stimulation (frequency, current, and duration of the stimulation train).2. The maximal amplitude gaze shifts, produced by electrical stimulation at 56 sites in the SC of two rhesus monkeys, ranged in amplitude from similar to 7 to similar to 80 deg. Because the head was unrestrained, stimulation-induced gaze shifts often included movements of the head. Head movements produced at the 56 stimulation sites ranged in amplitude from 0 to similar to 70 deg.3. The relationships between peak velocity and amplitude and between duration and amplitude of stimulation-induced head movements and gaze shifts were comparable with the relationships observed during visually guided gaze shifts. The relative contributions of the eyes and head to visually guided and stimulation-induced gaze shifts were also similar.4. As was true for visually guided gaze shifts, the head contribution to stimulation-induced gaze shifts depended on the position of the eyes relative to the head at the onset of stimulation. When the eyes were deviated in the direction of the ensuing gaze shift, the head contribution increased and the latency to head movement onset was decreased.5. We systematically altered the duration of stimulation trains (10-400 ms) while stimulation frequency and current remained constant. Increases in stimulation duration systematically increased the amplitude of the evoked gaze shift until a site specific maximal amplitude was reached. Further increases in stimulation duration did not increase gaze amplitude. There was a high correlation between the end of the stimulation train and the end of the evoked gaze shift for movements smaller than the site-specific maximal amplitude.6. Unlike the effects of stimulation duration on gaze amplitude; the amplitude and duration of evoked head movements did not saturate for the range of durations tested (10-400 ms), but continued to increase linearly with increases in stimulation duration.7. The frequency of stimulation was systematically varied (range: 63-1,000 Hz) while other stimulation parameters remained constant. The velocity of evoked gaze shifts was related to the frequency of stimulation; higher stimulation frequencies resulted in higher peak velocities. The maximal, site-specific amplitude was independent of stimulation frequency.8. When stimulating a single collicular site using identical stimulation parameters, the amplitude and direction of stimulation-induced gaze shifts, initiated from different initial positions, were relatively constant. In contrast, the amplitude and direction of the eye component of these fixed vector gaze shifts depended upon the initial position of the eyes in the orbits; the endpoints of the eye movements converged on an orbital region, or ''goal,'' that depended on the site of collicular stimulation.9. When identical stimulation parameters were used and when the eyes were centered initially in the orbits, the gaze shifts produced by caudal collicular stimulation when the head was restrained were typically smaller than those evoked from the same site when the head was unrestrained. This attenuation occurred because stimulation drove the eyes to approximately the same orbital position when the head was restrained or unrestrained. Thus movements produced when the head was restrained were reduced in amplitude by approximately the amount that the head would have contributed if free to move.10. When the head was restrained, only the eye component of the intended gaze shift was observed. This resulted in a dissociation of the ''desired'' gaze amplitude specified by the locus of collicular activity and the observed movement. Because, during head-restrained stimulation, the observed movement is only a portion of the movement encoded by the locus of collicular activity, the collicular ''motor map'' defined using microstimulation in head-restrained subjects may be distorted.11. The directions of the eye, head, and gaze components of stimulation-induced movements, evoked from different initial positions, were different. For example, during an oblique gaze shift directed 45 deg above the horizontal meridian, the eye component of the gaze shift could be almost purely vertical and the head component almost purely horizontal. This produced a dissociation of the eye, head and gaze movement directions.12. Collectively, these data are inconsistent with the hypothesis that the SC generates separate eye and head displacement commands. Instead, the findings are interpreted as support for the hypothesis that a signal of desired gaze displacement is derived from the locus of collicular activity. The level of collicular activity can influence the velocity of gaze shifts without affecting the graze displacement signal.