Neuronal networks for control of eye movement

中缝背核任务奖励值的编码：中缝背核及其血清素释放神经元被认为调节动机和奖励寻求。众所周知，这些神经元在动机行为中是活跃的，但控制它们活动的基本原理尚不清楚。在这里，我们展示了一组背中缝神经元以一种系统的方式编码行为任务，跟踪即将到来的奖励的进展。我们分析了动物在执行两个奖励导向的扫视任务时记录的背中缝神经元活动。在行为任务中神经元的紧张活动水平与其编码奖励相关线索和结果之间存在很强的相关性。在任务过程中被紧张性兴奋的神经元主要携带积极的奖励信号。在任务中被强直抑制的神经元主要携带负奖励信号。在任务中没有改变其紧张活动水平的神经元有较弱的奖励信号，没有正向或负向的倾向。这种形式的相关任务和奖励编码解释了我们任务中背缝反应模式的大部分系统性变化。神经活动的一个较小的组成部分反映了对奖励传递的检测。我们的数据表明，中缝背核根据其未来的动机结果编码参与行为任务。

Coding of task reward value in the dorsal raphe nucleus: The dorsal raphe nucleus and its serotonin-releasing neurons are thought to regulate motivation and reward-seeking. These neurons are known to be active during motivated behavior, but the underlying principles that govern their activity are unknown. Here we show that a group of dorsal raphe neurons encode behavioral tasks in a systematic manner, tracking progress toward upcoming rewards. We analyzed dorsal raphe neuron activity recorded while animals performed two reward-oriented saccade tasks. There was a strong correlation between the tonic activity level of a neuron during behavioral tasks and its encoding of reward-related cues and outcomes. Neurons that were tonically excited during the task predominantly carried positive reward signals. Neurons that were tonically inhibited during the task predominantly carried negative reward signals. Neurons that did not change their tonic activity levels during the task had weak reward signals with no tendency for a positive or negative direction. This form of correlated task and reward coding accounted for the majority of systematic variation in dorsal raphe response patterns in our tasks. A smaller component of neural activity reflected detection of reward delivery. Our data suggest that the dorsal raphe nucleus encodes participation in a behavioral task in terms of its future motivational outcomes. Distinct tonic and phasic anticipatory activity in lateral habenula and dopamine neurons: Dopamine has a crucial role in anticipation of motivational events. To investigate the underlying mechanisms of this process, we analyzed the activity of dopamine neurons and one of their major sources of input, neurons in the lateral habenula, while animals anticipated upcoming behavioral tasks. We found that lateral habenula and dopamine neurons anticipated tasks in two distinct manners. First, neurons encoded the timing distribution of upcoming tasks through gradual changes in their tonic activity. This tonic signal encoded rewarding tasks in preference to punishing tasks and was correlated with classic phasic coding of motivational value. Second, neurons transmitted a phasic signal marking the time when a task began. This phasic signal encoded rewarding and punishing tasks in similar manners, as though reflecting motivational salience. Our data suggest that the habenula-dopamine pathway motivates anticipation through a combination of tonic reward-related and phasic salience-related signals. Multiple timescales of memory in lateral habenula and dopamine neurons: Midbrain dopamine neurons are thought to signal predictions about future rewards based on the memory of past rewarding experience. Little is known about the source of their reward memory and the factors that control its timescale. Here we recorded from dopamine neurons, as well as one of their sources of input, the lateral habenula, while animals predicted upcoming rewards based on the past reward history. We found that lateral habenula and dopamine neurons accessed two distinct reward memories: a short-timescale memory expressed at the start of the task and a near-optimal long-timescale memory expressed when a future reward outcome was revealed. The short- and long-timescale memories were expressed in different forms of reward-oriented eye movements. Our data show that the habenula-dopamine pathway contains multiple timescales of memory and provide evidence for their role in motivated behavior.