Seeking the Neural Substrates of Visual Working Memory Storage

It is widely assumed that the prefrontal cortex (PFC) is a critical site of working memory storage in monkeys and humans. Recent reviews of the human lesion literature and recent neuroimaging results, however, challenge this view. To test these alternatives, we used event-related fMRI to trace the retention of working memory representation of target faces across three delay periods that were interposed between the presentation of each of four stimuli. Across subjects, only posterior fusiform gyrus demonstrated reliable retention of target-specific activity across all delay periods. Our results suggest that no part of frontal cortex, including PFC, stores mnemonic representation of faces reliably across distracted delay periods. Rather, working memory storage of faces is mediated by a domain- specific network in posterior cortex.