Evidence for multiple manipulation processes in prefrontal cortex

Dana A. Eldreth, Michael D. Patterson, Anthony J. Porcelli, Bharat B. Biswal, Donovan Rebbechi, Bart Rypma

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

The prefrontal cortex (PFC) is known to subserve working memory (WM) processes. Brain imaging studies of WM using delayed response tasks (DRTs) have shown memory-load-dependent activation increases in dorsal prefrontal cortex (PFC) regions. These activation increases are believed to reflect manipulation of to-be-remembered information in the service of memory-consolidation. This speculation has been based on observations of similar activation increases in tasks that overtly require manipulation by instructing participants to reorder to-be-remembered list items. In this study, we tested the assumption of functional equivalence between these two types of WM tasks. Participants performed a DRT under two conditions with memory loads ranging from 3 to 6 letters. In an "item-order" condition, participants were required to remember letters in the order in which they were presented. In a "reordering" condition, participants were required to remember the letters in alphabetical order. Load-related activation increases were observed during the encoding and maintenance periods of the order maintenance condition, whereas load-related activation decreases were observed in the same periods of the reordering condition. These results suggest that (1) the neural substrates associated with long-list retention and those associated with reordering are not equivalent, (2) cognitive processes associated with long-list retention may be more closely approximated by item-order maintenance than by reordering, and (3) multiple forms of WM manipulation are dissociable on the basis of fMRI data.

Original languageEnglish (US)
Pages (from-to)145-156
Number of pages12
JournalBrain Research
Volume1123
Issue number1
DOIs
StatePublished - Dec 6 2006
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

Keywords

  • Delayed response task
  • Prefrontal cortex
  • Working memory
  • fMRI

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