Watanabe Masataka, Hikosaka Kazuo, Sakagami Masamichi, Shirakawa Shu-Ichiro
Department of Psychology, Tokyo Metropolitan Institute for Neuroscience, Musashidai 2-6, Fuchu, Tokyo, 183-8526, Japan.
Exp Brain Res. 2005 Oct;166(2):263-76. doi: 10.1007/s00221-005-2358-y. Epub 2005 Jul 21.
The lateral prefrontal cortex (LPFC) is important in cognitive control. During the delay period of a working memory (WM) task, primate LPFC neurons show sustained activity that is related to retaining task-relevant cognitive information in WM. However, it has not yet been determined whether LPFC delay neurons are concerned exclusively with the cognitive control of WM task performance. Recent studies have indicated that LPFC neurons also show reward and/or omission-of-reward expectancy-related delay activity, while the functional relationship between WM-related and reward/omission-of-reward expectancy-related delay activity remains unclear. To clarify the functional significance of LPFC delay-period activity for WM task performance, and particularly the functional relationship between these two types of activity, we examined individual delay neurons in the primate LPFC during spatial WM (delayed response) and non-WM (reward-no-reward delayed reaction) tasks. We found significant interactions between these two types of delay activity. The majority of the reward expectancy-related neurons and the minority of the omission-of-reward expectancy-related neurons were involved in spatial WM processes. Spatial WM-related neurons were more likely to be involved in reward expectancy than in omission-of-reward expectancy. In addition, LPFC delay neurons observed during the delayed response task were not concerned exclusively with the cognitive control of task performance; some were related to reward/omission-of-reward expectancy but not to WM, and many showed more memory-related activity for preferred rewards than for less-desirable rewards. Since employing a more preferred reward induced better task performance in the monkeys, as well as enhanced WM-related neuronal activity in the LPFC, the principal function of the LPFC appears to be the integration of cognitive and motivational operations in guiding the organism to obtain a reward more effectively.
外侧前额叶皮质（LPFC）在认知控制中起着重要作用。在工作记忆（WM）任务的延迟期，灵长类动物的LPFC神经元会表现出持续活动，这种活动与在WM中保留与任务相关的认知信息有关。然而，LPFC延迟神经元是否仅与WM任务表现的认知控制有关，目前尚未确定。最近的研究表明，LPFC神经元还表现出与奖励和/或奖励缺失预期相关的延迟活动，而与WM相关的延迟活动和与奖励/奖励缺失预期相关的延迟活动之间的功能关系仍不清楚。为了阐明LPFC延迟期活动对WM任务表现的功能意义，特别是这两种活动类型之间的功能关系，我们在空间WM（延迟反应）和非WM（奖励-无奖励延迟反应）任务中检查了灵长类动物LPFC中的单个延迟神经元。我们发现这两种延迟活动之间存在显著的相互作用。大多数与奖励预期相关的神经元和少数与奖励缺失预期相关的神经元参与了空间WM过程。与空间WM相关的神经元更有可能参与奖励预期而不是奖励缺失预期。此外，在延迟反应任务中观察到的LPFC延迟神经元并非仅与任务表现的认知控制有关；一些与奖励/奖励缺失预期有关，但与WM无关，而且许多神经元对偏好奖励的记忆相关活动比对不太想要的奖励的活动更多。由于使用更偏好的奖励能使猴子的任务表现更好，同时增强LPFC中与WM相关的神经元活动，LPFC的主要功能似乎是整合认知和动机操作，以引导机体更有效地获得奖励。
