Abstract
Working memory has been commonly defined as temporary active storage mechanism of information. Although its definition differs from scientist to scientist, working memory can be considered as a dynamic system for retaining and processing information, which consists of 4 elementary processes ; an input/selection process, a temporary storage process, an output process, and a processing process of information. We have analyzed single-neuron activity in the prefrontal cortex while monkeys performed working memory tasks, and found that many neurons exhibited delay-period activity which lasted tonically during the delay period and showed preferences depending upon stored information. Therefore, delay-period activity is considered to reflect a temporary active storage process of information. In addition, we found cue-period activity and pre-movement activity, each of which may reflect an input/selection process and an output process, respectively. We also observed delay-period activity related to integrating multiple information and a feedback signal from a motor center (post-movement activity) to manipulate stored information. These latter results suggest that an interaction among prefrontal neurons is important for a processing process to integrate or manipulate information. Since working memory is a dynamic system for processing information, we need to further examine neuronal mechanisms of each elementary process as well as dynamic interactions among these processes to understand neuronal mechanisms of working memory.
