Optical imaging of short-term working memory in prefrontal cortex of the Macaque monkey

Prefrontal cortex is an area critical for cognitive functions such as planning, decision-making, and reasoning. Working memory is a key aspect to the execution of these functions and has been strongly associated with prefrontal function. This chapter reviews the functional organization of a prefrontal area, area 46, that has been associated with working memory in monkeys. Anatomical and optical imaging studies indicate the presence of a clustered organization within area 46, similar in nature to clustered organizations found in sensory cortical areas. Although the relationship of these clusters to working memory function is unknown, optical imaging studies suggest a spatial organization for mnemonic function. This 'spatial memory map' is topographically consistent with electrophysiologically established maps for visual and eye movement response. Interestingly, in trials in which response suppression is required, optical imaging reveals a possible suppressive signal; lack of this signal may underly the perseveration seen in diseases such as schizophrenia. In sum, I suggest that clustered organization in prefrontal cortex provides a scaffold upon which visual, mnemonic, and motor response are organized.