Physiological characteristics of capacity constraints in working memory as revealed by functional MRI

Joseph H. Callicott, Venkata S. Mattay, Alessandro Bertolino, Kimberly Finn, Richard Coppola, Joseph A. Frank, Terry E. Goldberg, Daniel R. Weinberger

Research output: Contribution to journalArticlepeer-review

Abstract

A fundamental characteristic of working memory is that its capacity to handle information is limited. While there have been many brain mapping studies of working memory, the physiological basis of its capacity limitation has not been explained. We identified characteristics of working memory capacity using functional magnetic resonance imaging (fMRI) in healthy subjects. Working memory capacity was studied using a parametric 'n-back' working memory task involving increasing cognitive load and ultimately decreasing task performance. Loci within dorsolateral prefrontal cortex (DLPFC) evinced exclusively an 'inverted-U' shaped neurophysiological response from lowest to highest load, consistent with a capacity-constrained response. Regions outside of DLPFC, in contrast, were more heterogeneous in response and often showed early plateau or continuously increasing responses, which did not reflect capacity constraints. However, sporadic loci, including in the promotor cortex, thalamus and superior parietal lobule, also demonstrated putative capacity-constrained responses, perhaps arising as an upstream effect of DLPFC limitations or as part of a broader network-wide capacity limitation. These results demonstrate that regionally specific nodes within the working memory network are capacity-constrained in the physiological domain, providing a missing link in current explorations of the capacity characteristics of working memory.

Original languageEnglish (US)
Pages (from-to)20-26
Number of pages7
JournalCerebral Cortex
Volume9
Issue number1
DOIs
StatePublished - 1999
Externally publishedYes

ASJC Scopus subject areas

  • Cognitive Neuroscience
  • Cellular and Molecular Neuroscience

Fingerprint

Dive into the research topics of 'Physiological characteristics of capacity constraints in working memory as revealed by functional MRI'. Together they form a unique fingerprint.

Cite this