Evidence for multiple manipulation processes in prefrontal cortex.
Brain Res
; 1123(1): 145-56, 2006 Dec 06.
Article
em En
| MEDLINE
| ID: mdl-17070786
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.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Tempo de Reação
/
Rememoração Mental
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Mapeamento Encefálico
/
Córtex Pré-Frontal
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Memória de Curto Prazo
Limite:
Adolescent
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Adult
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Female
/
Humans
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Male
Idioma:
En
Ano de publicação:
2006
Tipo de documento:
Article