Neuronal networks for control of eye movement

丘脑底核神经元在从自动眼球运动到控制眼球运动的转换中的作用：基底节的丘脑底核是运动控制的重要组成部分。STN损伤引起的不自主运动和STN刺激治疗帕金森病的成功证明了这一点。然而，目前尚不清楚单个STN神经元如何参与运动控制。在这里，我们发现STN具有从自动控制眼动切换到自愿控制眼动的功能。在训练过的猕猴的STN中，我们发现神经元的活动显示出阶段性变化，特别是在从自动眼跳切换到自愿控制的眼跳之前。大多数与开关相关的神经元被认为抑制了不再有效的自动过程，这种抑制足够早地开始，使动物能够进行开关。我们认为，STN通过与其他基底节核团和上丘的联系，介导来自额叶内侧皮质的控制信号，并实现行为转换功能。 中缝背核神经元活动的奖赏依赖性调节：多巴胺系统被认为在基于奖赏的行为指导中发挥核心作用。最近的药理学研究表明，另一种单胺类神经递质5-羟色胺也参与了奖赏过程。为了阐明5-羟色胺神经元和多巴胺神经元之间的功能关系，我们在中缝背核(5-羟色胺的主要来源)和黑质致密部(多巴胺的主要来源)进行了单位记录，而猴子则执行跳视任务，其中目标的位置指示了即将到来的奖励的大小。在靶点启动后，但在奖赏发放之前，许多DRN神经元的活动受到具有大或小奖赏偏好的预期奖赏大小的调节，而假定的多巴胺神经元具有相性反应，只喜欢大奖赏。在奖赏传递后，DRN神经元的活动被具有大或小奖赏偏好的接收奖赏大小调节，而多巴胺神经元的活动不被调节，除非位置奖赏偶发事件发生意外逆转。因此，DRN神经元编码预期和收到的奖励，而多巴胺神经元编码预期和收到的奖励之间的差异。这些结果表明，DRN可能包括5-羟色胺神经元，发出与当前行为相关的奖赏价值的信号。

Role for the subthalamic nucleus neurons in switching from automatic to controlled eye movement: The subthalamic nucleus (STN) of the basal ganglia is an important element of motor control. This is demonstrated by involuntary movements induced by STN lesions and the successful treatment of Parkinsons disease by STN stimulation. However, it is still unclear how individual STN neurons participate in motor control. Here, we found that the STN has a function in switching from automatic to volitionally controlled eye movement. In the STN of trained macaque monkeys, we found neurons that showed a phasic change in activity specifically before volitionally controlled saccades which were switched from automatic saccades. A majority of switch-related neurons were considered to inhibit no-longer-valid automatic processes, and the inhibition started early enough to enable the animal to switch. We suggest that the STN mediates the control signal originated from the medial frontal cortex and implements the behavioral switching function using its connections with other basal ganglia nuclei and the superior colliculus. Reward-dependent modulation of neuronal activity in the dorsal raphe nucleus: The dopamine system has been thought to play a central role in guiding behavior based on rewards. Recent pharmacological studies suggest that another monoamine neurotransmitter, serotonin, is also involved in reward processing. To elucidate the functional relationship between serotonin neurons and dopamine neurons, we performed single-unit recording in the dorsal raphe nucleus (DRN), a major source of serotonin, and the substantia nigra pars compacta, a major source of dopamine, while monkeys performed saccade tasks in which the position of the target indicated the size of an upcoming reward. After target onset, but before reward delivery, the activity of many DRN neurons was modulated tonically by the expected reward size with either large- or small-reward preference, whereas putative dopamine neurons had phasic responses and only preferred large rewards. After reward delivery, the activity of DRN neurons was modulated tonically by the received reward size with either large- or small-reward preference, whereas the activity of dopamine neurons was not modulated except after the unexpected reversal of the positionreward contingency. Thus, DRNneurons encode the expected and received rewards, whereas dopamine neurons encode the difference between the expected and received rewards. These results suggest that the DRN, probably including serotonin neurons, signals the reward value associated with the current behavior.