The influence of working-memory demand and subject performance on prefrontal cortical activity

Bart Rypma, Jeffrey S. Berger, Mark D'Esposito

Research output: Contribution to journalArticle

275 Citations (Scopus)

Abstract

Brain imaging and behavioral studies of working memory (WM) converge to suggest that the ventrolateral prefrontal cortex (PFC) mediates a capacity-limited storage buffer and that the dorsolateral PFC mediates memory organization processes that support supracapacity memory storage. Previous research from our laboratory has shown that the extent to which such memory organization processes are required depends on both task factors (i.e., memory load) and subject factors (i.e., response speed). Task factors exert their effects mainly during WM encoding while subject factors exert their effects mainly during WM retrieval. In this study, we sought to test the generalizability of these phenomena under more difficult memory-demand conditions than have been used previously. During scanning, subjects performed a WM task in which they were required to maintain between 1 and 8 letters over a brief delay. Neural activity was measured during encoding, maintenance, and retrieval task periods using event-related functional magnetic resonance imaging. With increasing memory load, there were reaction time increases and accuracy rate decreases, ventrolateral PFC activation decreases during encoding, and dorsolateral PFC activation increases during maintenance and retrieval. These results suggest that the ventrolateral PFC mediates WM storage and that the dorsolateral PFC mediates strategic memory organization processes that facilitate supracapacity WM storage. Additionally, high-performing subjects showed overall less activation than low-performing subjects, but activation increases with increasing memory load in the lateral PFC during maintenance and retrieval. Low-performing subjects showed overall more activation than high-performing subjects, but minimal activation increases in the dorsolateral PFC with increasing memory load. These results suggest that individual differences in both neural efficiency and cognitive strategy underlie individual differences in the quality of subjects' WM performance.

Original languageEnglish (US)
Pages (from-to)721-731
Number of pages11
JournalJournal of Cognitive Neuroscience
Volume14
Issue number5
DOIs
StatePublished - Jul 1 2002

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Short-Term Memory
Prefrontal Cortex
demand
performance
activation
Maintenance
Individuality
Working Memory
organization
Neuroimaging
Reaction Time
Activation
Buffers
Magnetic Resonance Imaging
Efficiency
Research
brain

ASJC Scopus subject areas

  • Language and Linguistics
  • Linguistics and Language
  • Cognitive Neuroscience

Cite this

The influence of working-memory demand and subject performance on prefrontal cortical activity. / Rypma, Bart; Berger, Jeffrey S.; D'Esposito, Mark.

In: Journal of Cognitive Neuroscience, Vol. 14, No. 5, 01.07.2002, p. 721-731.

Research output: Contribution to journalArticle

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