title: A parametric study of prefrontal cortex involvement in human working memory.
abstract: Although recent neuroimaging studies suggest that prefrontal cortex (PFC) is involved in working memory (WM), the relationship between PFC activity and memory load has not yet been well-described in humans. Here we use functional magnetic resonance imaging (fMRI) to probe PFC activity during a sequential letter task in which memory load was varied in an incremental fashion. In all nine subjects studied, dorsolateral and left inferior regions of PFC were identified that exhibited a linear relationship between activity and WM load. Furthermore, these same regions were independently identified through direct correlations of the fMRI signal with a behavioral measure that indexes WM function during task performance. A second experiment, using whole-brain imaging techniques, both replicated these findings and identified additional brain regions showing a linear relationship with load, suggesting a distributed circuit that participates with PFC in subserving WM. Taken together, these results provide a "dose-response curve" describing the involvement of both PFC and related brain regions in WM function, and highlight the benefits of using graded, parametric designs in neuroimaging research.
authors.affiliation: Department of Psychology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Braver
authors.forename: J D
authors.initials: JD
authors.lastname: Cohen
authors.forename: L E
authors.initials: LE
authors.lastname: Nystrom
authors.forename: J
authors.initials: J
authors.lastname: Jonides
authors.forename: E E
authors.initials: EE
authors.lastname: Smith
authors.forename: D C
authors.initials: DC
authors.lastname: Noll
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology; D001931:Brain Mapping / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation; D007206:Individuality; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D014706:Verbal Learning / Q000502:physiology