Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, CO 80045, United States of America; Neuroscience Program, University of Colorado School of Medicine, Aurora, CO 80045, United States of America; Medical Scientist Training Program, University of Colorado School of Medicine, Aurora, CO 80045, United States of America.
Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, CO 80045, United States of America; Neuroscience Program, University of Colorado School of Medicine, Aurora, CO 80045, United States of America.
Neuroscience. 2019 Jun 1;408:191-203. doi: 10.1016/j.neuroscience.2019.04.002. Epub 2019 Apr 11.
Selecting and moving to spatial targets are critical components of goal-directed behavior, yet their neural bases are not well understood. The superior colliculus (SC) is thought to contain a topographic map of contralateral space in which the activity of specific neuronal populations corresponds to particular spatial locations. However, these spatial representations are modulated by several decision-related variables, suggesting that they reflect information beyond simply the location of an upcoming movement. Here, we examine the extent to which these representations arise from competitive spatial choice. We recorded SC activity in male mice performing a behavioral task requiring orienting movements to targets for a water reward in two contexts. In "competitive" trials, either the left or right target could be rewarded, depending on which stimulus was presented at the central port. In "noncompetitive" trials, the same target (e.g., left) was rewarded throughout an entire block. While both trial types required orienting movements to the same spatial targets, only in competitive trials do targets compete for selection. We found that in competitive trials, pre-movement SC activity predicted movement to contralateral targets, as expected. However, in noncompetitive trials, some neurons lost their spatial selectivity and in others activity predicted movement to ipsilateral targets. Consistent with these findings, unilateral optogenetic inactivation of pre-movement SC activity ipsiversively biased competitive, but not noncompetitive, trials. Incorporating these results into an attractor model of SC activity points to distinct pathways for orienting movements under competitive and noncompetitive conditions, with the SC specifically required for selecting among multiple potential targets.
选择和移动到空间目标是目标导向行为的关键组成部分，但它们的神经基础还不是很清楚。上丘（SC）被认为包含了一个对侧空间的地形图，其中特定神经元群体的活动对应于特定的空间位置。然而，这些空间表示受到几个与决策相关的变量的调节，这表明它们反映的信息不仅仅是即将进行的运动的位置。在这里，我们研究了这些表示在多大程度上来自竞争性的空间选择。我们在执行需要在两个环境中向目标定向运动以获得水奖励的行为任务的雄性小鼠中记录了 SC 的活动。在“竞争”试验中，左或右目标可以根据中央端口呈现的刺激而得到奖励。在“非竞争”试验中，相同的目标（例如左）在整个块中都得到奖励。虽然两种试验类型都需要将运动导向相同的空间目标，但只有在竞争试验中，目标才会竞争选择。我们发现，在竞争试验中，运动前 SC 的活动如预期那样预测了对侧目标的运动。然而，在非竞争试验中，一些神经元失去了它们的空间选择性，而在其他神经元中，活动预测了同侧目标的运动。与这些发现一致，单侧光遗传失活运动前 SC 的活动对竞争试验产生了偏向作用，但对非竞争试验没有影响。将这些结果纳入 SC 活动的吸引子模型表明，在竞争和非竞争条件下，定向运动有不同的途径，SC 专门用于从多个潜在目标中进行选择。
