Vision Performance Institute, College of Optometry, Pacific University, Forest Grove, OR 97116, USA.
J Neurophysiol. 2010 May;103(5):2458-69. doi: 10.1152/jn.00215.2009. Epub 2010 Feb 17.
Animals depend on learned rules to guide their actions. Prefrontal (PFC) and premotor (PMC) cortex of primates have been reported to display rule-related neural activity, but it is unclear how signals encoded here are utilized to enforce the decision to act. The supplementary eye field (SEF) is a candidate for enforcing rule-guided ocular decisions because the activity of neurons here is correlated with the rule in an ocular decision-making task and because this area is anatomically more proximal to movement structures than PFC and PMC and receives inputs from them. However, in the previous work, the rule encoding and ocular outcome were confounded, leaving open the question of whether SEF activity is related to the rule or the behavior. In the present study, we attempted to discriminate between these alternatives by increasing task difficulty and forcing errors, thereby putting the stimulus and the behavior at odds. Single SEF neurons were recorded while monkeys performed the task in which the rule is to pursue a moving target if it intersects a visible square and maintain fixation if it does not. A delay period was imposed to monitor neural activity while the target approached the square. Two complementary populations of go and nogo neurons were found. When task difficulty was increased, the monkeys made more errors, and the neurons took longer to encode the rule. However, in error trials, most neurons continued to reflect the rule rather the monkey's ocular decision in both the delay period and after square intersection (movement period). This was the case for both directionally tuned and nondirectional SEF neurons. The results suggest that SEF neurons encode the ocular decision rule but that the decision itself likely occurs in a different structure that sums rule information from the SEF with information from other areas.
动物依靠习得的规则来指导它们的行为。灵长类动物的前额叶皮层（PFC）和前运动皮层（PMC）被报道显示出与规则相关的神经活动，但尚不清楚这里编码的信号如何被用来执行行动的决定。补充眼区（SEF）是执行规则引导的眼球决策的候选区域，因为这里的神经元活动与眼球决策任务中的规则相关，并且由于该区域在解剖学上比 PFC 和 PMC 更接近运动结构，并且接收来自它们的输入。然而，在之前的工作中，规则编码和眼球结果是混淆的，这使得 SEF 活动是与规则还是行为相关的问题仍然存在。在本研究中，我们试图通过增加任务难度和强制错误来区分这些替代方案，从而使刺激和行为产生冲突。当猴子执行任务时，我们记录了单个 SEF 神经元的活动，任务规则是如果移动目标与可见正方形相交，则追踪它，如果不相交，则保持注视。在目标接近正方形期间施加延迟期以监测神经活动。发现了两种互补的 Go 和 NoGo 神经元群体。当任务难度增加时，猴子犯的错误更多，神经元需要更长的时间来编码规则。然而，在错误试验中，大多数神经元在延迟期和正方形交叉后（运动期）继续反映规则而不是猴子的眼球决策。方向性和非方向性 SEF 神经元都是如此。结果表明，SEF 神经元编码眼球决策规则，但决策本身可能发生在另一个结构中，该结构将来自 SEF 的规则信息与来自其他区域的信息相加。
