Many organisms show an impressive capacity to store information for online recall in the performance of memory tasks (Goldman-Rakic, 1990). This rapid and temporary storage of information during an experimental trial has been called “working memory.” In many behavioral paradigms, individual cells in the prefrontal and medial temporal lobe cortices show persistent firing in the absence of continued sensory input. This persistent activity is thought to form the neural basis for working memory behaviors (Goldman-Rakic, 1995).