Neuronal networks for control of eye movement

辅助前运动区（pre-SMA）在克服自动眼动中的作用：我们和其他实验室先前的数据表明，内侧额叶皮层的一部分称为前sma在改变行动计划或任务切换中起着重要作用。我们假设，在基于自动过程的动作选择不利的情况下，sma前在产生期望的运动动作中起作用。为了验证这一假设，我们记录了一只猴子执行扫视任务时前sma的神经元活动，在这个任务中，猴子不得不偶尔从自动行为切换到控制行为。我们发现，在前驱期，许多前sma细胞选择性地改变了它们在颜色转换试验中的放电。当我们在提示开始时电微刺激前sma时，开关试验的正确率显着增加。这些数据支持我们的假设，即sma前在克服自动动作生成以启动新所需动作方面起关键作用。我们目前正在测试一个扩展的假设，即前sma通过投射到基底神经节来执行其开关功能。

Role of the pre-supplementary motor area (pre-SMA) in the overcoming of automatic eye movements: Preceding data from our and other laboratories have suggested that a part of the medial frontal cortex called the pre-SMA plays an important role in changing action plans or task switching. We hypothesized that the pre-SMA plays a role in generating desired motor acts in situations where the selection of action based on automatic processes is unfavorable. To test this hypothesis, we recorded neuronal activity in the pre-SMA of a monkey performing a saccade task in which the monkey had to occasionally switch from automatic to controlled behavior. We found that, during a presaccadic period, many pre-SMA cells selectively changed their firing on color-switch trials. When we electrically microstimulated the pre-SMA at cue onset, the correct rate on switch trials increased significantly. These data support our hypothesis that the pre-SMA plays a key part in the overcoming of automatic action generation to initiate a newly required action. We are currently testing an extended hypothesis that the pre-SMA executes its switching function through its projection to the basal ganglia. Role of the primate lateral habenula in negative motivational control of oculomotor behavior: Although the absence of dopamine in the striatum leads to severe deficits in body movements as seen in Parkinsons disease, recent studies indicate that dopamine neurons carry reward-related, not movement-related, signals. However, it was unclear which parts of the brain provide dopamine neurons with signals necessary for these actions. We hypothesized that the lateral habenula is an important source of the reward signals. To test this hypothesis, we recorded the activity of habenula neurons and dopamine neurons while monkeys were performing a visually guided saccade task with positionally biased reward outcomes. A majority of habenula neurons were excited by a noreward-predicting target and inhibited by a reward-predicting target. In contrast, dopamine neurons were excited and inhibited by reward-predicting and noreward-predicting targets, respectively. Each time the rewarded and unrewarded positions were reversed, both habenula and dopamine neurons reversed their responses as the bias in saccade latency reversed. In unrewarded trials, the excitation of habenula neurons started earlier than the inhibition of dopamine neurons. Furthermore, weak electrical stimulation inside, not outside, the habenula elicited strong inhibitions in dopamine neurons. These results suggest that the lateral habenula guides the basal ganglia to suppress less rewarding saccadic eye movements by inhibiting dopamine neurons.