There is converging functional neuroimaging evidence for the involvement of the sustained activity in the prefrontal cortex underlying the process of working memory during the delay period in a working memory task. And due to the fact that the PFC has a lot of cortico-cortico connections and coritco-subcortico connections, it might be the case that these different connections probably mediate different component processes of working memory. It has been believed for example the the cortical network might mediate the maintenance of goals, while the subcortical networks mediates response selection and motor control