Abstract
Whereas brain studies of symbol manipulations, including thinking and tool-use, have been extensively performed in human with brain-imaging techniques, neuronal data for this issue have been limited. However, recent studies with monkeys have provided some interesting data that allow us to hypothesize neuronal mechanisms of symbol manipulations. For example, neuronal groups of the prefrontal cortex code and retain behavioral meaning/abstract information for guiding goal-directed motor acts. These neurons appear to play a role in manipulating and retaining of symbolic information. Further, the prefrontal cortex is well known as a center of working memory, which contains “executive” associated with manipulation of information and control of brain systems. Based on these and other findings, we can hypothesize that the prefrontal cortex has a neuronal system for “executive symbol manipulation”. The executive is a central neuronal system of goal-directed symbol manipulations for controlling other brain systems, and this system would first evolve for tool-use and eventually develop for language and other symbol manipulations. Since the executive symbol manipulation is a possible neuronal system of the prefrontal cortex and can be examined with non-human primates, this hypothesis would be useful for leading neuronal studies of brain mechanisms of symbol manipulations.
