NEURONAL ACTIVITY OF THE PREFRONTAL CORTEX IN RELATION TO TIME CODING.

本研究的目的是探讨前额叶皮层神经元活动是如何参与时间编码的。为了回答这个问题，我们首先记录了猴子在执行时间段创建任务时前额皮质的神经元活动，并训练猴子创建三个不同的时间段（2、4和8秒）。通过按下连接在前肢支架末端的保持键开始每次试验。按键后1 - 2秒，三个指示灯中的一个亮起2秒，每个指示灯指示灯亮起至保持键释放之间的最短等待时间。黄灯、红灯和绿色灯分别表示2秒、4秒和8秒的最短等待时间。此外，我们还应用了颠倒规则，其中绿色和红色灯的含义是颠倒的。即，绿色灯表示8秒的最小等待时间，红色灯表示4秒。这项任务是以块的方式执行的。每个区组由5个试验组成。在新的区块开始之前，通过灯随机闪烁2秒来指示反向规则。在前额叶皮层，大约70%的任务相关神经元在光照开始和运动开始之间的间隔期间是活跃的。许多前额叶皮层神经元在光照开始后表现出显著的活动增加或在整个等待期间表现出相对恒定的活动。大量的前额叶皮层神经元表现出不同的活动之间的2，4，和8等待期。部分前额叶皮层神经元在4秒和8秒等待时间内的活动强度在相同等待时间内存在着相反的规律。这些观察结果表明，前额叶皮层在执行这项任务中起着重要的作用，需要估计和测量不同的时间段。

The purpose of the present study was to examine how neuronal activity in the prefrontal cortex is involved in the time cording. For the first step to answer this question, we recorded neuronal activity in the prefrontal cortex during the performance of time period creation task.The monkey (Macaca fuscata) was trained to create the three different time periods (2, 4 or 8 sec). Each trial was started by pressing the hold key attached at the end of the forelimb brace. One to two seconds after the key press, one of the three lights was turned on for 2 sec, each of which indicating the minimum waiting period between the light onset to the hold key release. Yellow, red and green lights means 2, 4 and 8 sec of minimum waiting period, respectively. In addition, we also applied reversed rule, where the meaning of green and red lights was reversed. That is, green light indicated 8 sec of minimum waiting period and red light, 4 sec. This task was performed in a block manner. Each block consisted of 5 trials. Reversed rule was indicated by the lights flashed randomly for 2 sec, before the start of new block. The correct movement was rewarded with a drop of fruit juice (0.1 ml).In prefrontal cortex, about 70% of task-related neurons were active during the interval between the light onset and the initiation of movement Many prefrontal cortex neurons showed marked increased activity just after the light onset or relatively constant activity throughout the waiting period. A substantial number of prefrontal cortex neurons showed different activity between 2, 4, and 8 waiting periods. In some prefrontal cortex neurons, the magnitude of activity in 4 or 8 sec waiting period was different in the same waiting period in reversed rule. These observations indicate that the prefrontal cortex plays an important role in the execution of this task requiring to estimate and measure the different time periods.