The neural control of disjunctive saccades

我们自然而然地将目光重新定位到位于不同偏僻和深度的感兴趣目标。然而，大脑如何确保对双目定位的精确控制仍然存在很大争议。目的：本研究的主要目的是了解大脑是如何产生分离性眼跳的。在我们最近的工作中，我们已经证明了脑干眼跳发生器的神经元，通常被认为是纯共轭前运动驱动的来源，实际上在分离的眼跳过程中提供了时间上适当的会聚信息来驱动眼球运动。在目前的提案中，我们将把这项工作带入下一阶段，并确定运动前眼跳神经元收敛相关信号的来源。一个明显的候选者是上丘，它接受来自视差敏感皮质区域的输入，例如额叶眼场。运动前扫视神经元的额外收敛输入可能来自小脑和/或其深层核团。特别是，动眼蠕虫和尾侧顶核有重要的投射到运动前眼跳区域，并含有与眼跳有关的神经元放电。最后，中脑中的神经元，如收敛速度神经元，只有在平稳收敛时才有特征，也可能通过直接投射到眼外运动神经元，在驱动分离性眼跳方面发挥作用。这些可能性中的每一种都将被系统地探索。科学方法：警觉的猴子的单个神经元的活动将在警觉的猴子的扫视-集中交互过程中被量化。我们实验室开发的系统识别技术将被用来描述神经元在共轭和析取运动中的放电动力学。结果数据将在眼球运动系统的现有模型的背景下进行解释。实验意义：结果将被用来生成控制眼跳促进的收敛的网络的理论模型。这些模型反过来将提供一个基础，可以用来理解大脑如何协调多块肌肉的运动，以产生更复杂的自愿运动。

We naturally reorient our eyes to targets of interest located at different eccentricities and depths. However how the brain ensures the precise control of binocular positioning remains highly controversial.Objective: The main objective of this study is to understand how the brain generates disjunctive saccades. In our recent work, we have shown that the neurons of the brainstem saccadic generator, which are typically considered a source of purely conjugate premotor drive, in fact provide temporally appropriate vergence information to drive eye motion during disjunctive saccades. In the present proposal, we will take this work to the next stage and identify the source of the vergence-related signals of premotor saccadic neurons. One obvious candidate is the superior colliculus, which receives inputs from disparity sensitive cortical regions such as the frontal eye fields. Additional vergence inputs to premotor saccadic neurons could come from the cerebellum and/or its deep nuclei. In particular, the oculomotor vermis and caudal fastigial nucleus have important projections to the premotor saccadic region and contain neurons whose discharges are related to saccades. Finally, neurons in the midbrain such as vergence-velocity neurons, which have only been characterized during smooth vergence, may also play a role in driving disjunctive saccades by means of their direct projections to the extraocular motoneurons. Each of these possibilities will be systematically explored.Scientific Approach: The activity of single neurons in alert behaving monkeys will be quantified during saccade-vergence interactions in alert behaving monkeys. System identification techniques developed in our laboratory will be used to describe the discharge dynamics of neurons during conjugate and disjunctive movements. The resultant data will be interpreted in the context of current models of the oculomotor system.Experimental Significance: Results will be used to generate theoretical models of the networks that control saccade-facilitated vergence.  These models will, in turn, provide a foundation that can be used to understand how the brain coordinates the movement of multiple muscles to generate more complex voluntary movements.