Mushiake H, Fujii N, Tanji J
Department of Physiology, Tohoku University School of Medicine, Sendai, 980, Japan.
J Neurophysiol. 1999 Mar;81(3):1443-8. doi: 10.1152/jn.1999.81.3.1443.
We compared the effects of intracortical microstimulation (ICMS) of the lateral wall of the intraparietal sulcus (LIP) with those of ICMS of the frontal eye field (FEF) on monkeys performing oculomotor tasks. When ICMS was applied during a task that involved fixation, contraversive saccades evoked in the LIP and FEF appeared similar. When ICMS was applied to the FEF at the onset of voluntary saccades, the evoked saccades collided with the ongoing voluntary saccade so that the trajectory of voluntary saccade was compensated by the stimulus. Thus the resultant saccade was redirected and came close to the endpoint of saccades evoked from the fixation point before the start of voluntary saccade. In contrast, when ICMS was applied to the LIP at the onset of voluntary saccades, the resultant saccade followed a trajectory that was different from that evoked from the FEF. In that case, the colliding saccades were redirected toward an endpoint that was close to the endpoint of saccades evoked when animals were already fixating at the target of the voluntary saccade. This finding suggests that the colliding saccade was directed toward an endpoint calculated with reference to the target of the voluntary saccade. We hypothesize that, shortly before initiation of voluntary saccades, a dynamic process occurs in the LIP so that the reference point for calculating the saccade target shifts from the fixation point to the target of a voluntary saccade. Such predictive updating of reference points seems useful for immediate reprogramming of upcoming saccades that can occur in rapid succession.
我们比较了在猴子执行眼球运动任务时，顶内沟外侧壁（LIP）的皮质内微刺激（ICMS）与额叶眼区（FEF）的ICMS的效果。当在涉及注视的任务中施加ICMS时，LIP和FEF诱发的对侧扫视看起来相似。当在自主扫视开始时对FEF施加ICMS时，诱发的扫视与正在进行的自主扫视相撞，从而使自主扫视的轨迹因刺激而得到补偿。因此，最终的扫视被重新定向，并接近在自主扫视开始前从注视点诱发的扫视的终点。相比之下，当在自主扫视开始时对LIP施加ICMS时，最终的扫视遵循的轨迹与FEF诱发的不同。在这种情况下，相撞的扫视被重新定向到一个终点，该终点接近动物已经注视自主扫视目标时诱发的扫视的终点。这一发现表明，相撞的扫视是朝着参照自主扫视目标计算出的终点方向。我们假设，在自主扫视开始前不久，LIP中会发生一个动态过程，使得计算扫视目标的参考点从注视点转移到自主扫视的目标。这种参考点的预测性更新似乎有助于对可能快速连续发生的即将到来的扫视进行即时重新编程。
