Working memory for letters, shapes, and locations: fMRI evidence against stimulus-based regional organization in human prefrontal cortex

Leigh E. Nystrom, Todd S. Braver, Fred W. Sabb, Mauricio R. Delgado, Douglas C. Noll, Jonathan D. Cohen

Research output: Contribution to journalArticle

301 Scopus citations

Abstract

Investigations of working memory (WM) systems in the frontal cortex have revealed two stimulus dimensions along which frontal cortical representations may be functionally organized. One hypothesized dimension dissociates verbal from nonverbal WM processes, dividing left from right frontal regions. The second hypothesized dimension dissociates spatial from nonspatial WM, dividing dorsal from ventral frontal regions. Here we used functional magnetic resonance imaging to probe WM processes associated with three different types of stimuli: letters (verbal and nonspatial), abstract shapes (nonverbal and nonspatial), and locations (nonverbal and spatial). In a series of three experiments using the 'n-back' WM paradigm, direct statistical comparisons were made between activation patterns in each pairwise combination of the three stimulus types. Across the experiments, no regions that demonstrated responses to WM manipulations were discovered to be unique to any of the three stimulus types. Therefore, no evidence was found to support either a left/right verbal/nonverbal dissociation or a dorsal/ventral spatial/nonspatial dissociation. While this could reflect a limitation of the present behavioral and imaging techniques, other factors that could account for the data are considered, including subjects' strategy selection, encoding of information into WM, and the nature of representational schemes in prefrontal cortex. (C) 2000 Academic Press.

Original languageEnglish (US)
Pages (from-to)424-446
Number of pages23
JournalNeuroimage
Volume11
Issue number5 I
DOIs
StatePublished - May 2000

All Science Journal Classification (ASJC) codes

  • Neurology
  • Cognitive Neuroscience

Fingerprint Dive into the research topics of 'Working memory for letters, shapes, and locations: fMRI evidence against stimulus-based regional organization in human prefrontal cortex'. Together they form a unique fingerprint.

  • Cite this