title: Dissociable contributions of prefrontal cortex and the hippocampus to short-term memory: evidence for a 3-state model of memory.
abstract: Behavioral research has yielded conflicting results regarding the architecture of short-term memory (STM). Whereas a consensus has emerged that within STM a single chunk within the focus of attention (FA) has a privileged status, it is unclear whether further distinctions exist. One proposal is that outside of FA, memory is all of one sort with a continuous progression from STM to long-term memory (LTM). On the other hand, sharp performance drop-offs when STM is loaded with more than 4±1 items suggest distinctions between STM and LTM. We use functional magnetic resonance imaging (fMRI) to adjudicate between these theories. A neural triple dissociation provided evidence for a 3-state model of memory. Critically, prefrontal cortex was selectively enhanced to retrieval from activated portions of LTM whereas the hippocampus was associated with retrieval of items within putative 4±1 capacity limits. We hypothesize that the associative properties of the hippocampus serve to inter-relate information actively maintained in STM which not only promotes strong STM, but also lays the foundations for subsequent LTM. By contrast, information not actively maintained in mind requires top-down retrieval processes mediated by the prefrontal cortex. These data provide key insights into the architecture of STM and its relationship to LTM.
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA. denee@indiana.edu
authors.forename: Derek Evan
authors.initials: DE
authors.lastname: Nee
authors.forename: John
authors.initials: J
authors.lastname: Jonides
mesh_terms: D000328:Adult; D001931:Brain Mapping; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008959:Models, Neurological; D017397:Prefrontal Cortex / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D055815:Young Adult