Search for neuronal mechanisms related to thinking using flexible representation of various information on the nervous system

当猴子执行两个空间工作记忆任务(ODR和R-ODR任务)时，我们从前额叶皮质收集单个神经元活动，并使用所有收集的单个神经元活动构建种群载体。由线索和反应期活动构建的群体向量与视觉线索和眼跳的方向相似，表明这些群体向量代表了关于视觉线索和眼跳方向的信息。基于这些结果，我们得到了在延迟期内每50ms移动一次的250ms时间窗口内的布居向量。在ODR任务中，所有种群向量的方向与视觉线索的方向相似。然而，在R-ODR任务中，群体向量在从线索方向到扫视方向的延迟期内逐渐旋转。为了了解R-ODR任务中种群向量旋转所必需的神经元机制，我们研究了两种延迟期活动的时间模式；一种编码线索位置，另一种编码扫视方向。我们观察到编码眼跳方向的延迟期活动比编码线索位置的活动迅速增加，并发现这种增加的时间过程与R-ODR任务中种群向量的旋转开始相吻合。这些结果表明，在空间工作记忆任务中处理的信息可以被描述为种群向量中方向的时间变化。这些结果还表明，思维中的信息处理对应于从代表一种信息的一组神经元活动逐渐过渡到代表另一种信息的一组神经元活动。

We collected single-neuron activities from the prefrontal cortex while monkeys performed two spatial working memory tasks (ODR and R-ODR tasks) and constructed population vectors using all collected single-neuron activities. Population vectors constructed from cue- and response-period activity showed similar directions to the directions of the visual cues and the saccades in both tasks, indicating that these population vectors represent information regarding the direction of the visual cue and the direction of the saccade. Based on these results, we obtained population vectors during the 250 ms time window shifting every 50 ms during the delay period. In the ODR task, all population vectors were directed similar to the direction of the visual cue. However, in the R-ODR task, population vector rotated gradually during the delay period from the cue direction to the saccade direction. To understand neuronal mechanisms essential for the rotation of population vectors in the R-ODR task, we examined temporal patterns of two kinds of delay-period activity ; one encoding the cue location and the other encoding the saccade direction. We observed the rapid increase of delay-period activity encoding the saccade direction over the activity encoding the cue location, and found that the time course of this increase coincided with the initiation of rotation in population vectors in the R-ODR task. These results indicate that the information processed during spatial working memory tasks can be depicted as the temporal change of the direction in population vectors. These results also indicate that information processing during thinking corresponds to the gradual transition from a population of neuronal activities representing one kind of information to a population of neuronal activities representing other kind of information.