Recruitment of anterior and posterior structures in lexical-semantic processing: an fMRI study comparing implicit and explicit tasks.

Full Abstract

Previous studies examining explicit semantic processing have consistently shown activation of the left inferior frontal gyrus (IFG). In contrast, implicit semantic processing tasks have shown activation in posterior areas including the superior temporal gyrus (STG) and the middle temporal gyrus (MTG) with less consistent activation in the IFG. These results raise the question whether the functional role of the IFG is related to those processes needed to make a semantic decision or to processes involved in the extraction and analysis of meaning. This study examined neural activation patterns during a semantic judgment task requiring overt semantic analysis, and then compared these activation patterns to previously obtained results using the same semantically related and unrelated word pairs in a lexical decision task which required only implicit semantic processing (Rissman, J., Eliassen, J. C., & Blumstein, S. E. (2003). An event-related fMRI investigation of implicit semantic priming. Journal of Cognitive Neuroscience, 15, 1160-1175). The behavioral results demonstrated that the tasks were equivalent in difficulty. fMRI results indicated that the IFG and STG bilaterally showed greater activation for semantically unrelated than related word pairs across the two tasks. Comparison of the two task types across conditions revealed greater activation for the semantic judgment task only in the STG bilaterally and not in the IFG. These results suggest that the pre-frontal cortex is recruited similarly in the service of both the lexical decision and semantic judgment tasks. The increased activation in the STG in the semantic judgment task reflects the greater depth of semantic processing required in this task and indicates that the STG is not simply a passive store of lexical-semantic information but is involved in the active retrieval of this information.

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Author information

Author/s: Ruff, Ilana (I); Blumstein, Sheila E (SE); Myers, Emily B (EB); Hutchison, Emmette (E);

Affiliation: Department of Cognitive and Linguistic Sciences, Brown University, 190 Thayer Street, Box 1978, Providence, RI 02912, USA.

Grants: R01 DC00142 (Agency:United States NIDCD)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't

Journal: Brain and language (Brain Lang), published in United States. (Language: eng)

Reference: 2008-Apr; vol 105 (issue 1) : pp 41-9

Dates: Created 2008/03/24; Completed 2008/07/08;

PMID: 18279947, status: MEDLINE (last retrieval date: 11/6/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Brain Mapping
Comprehension - physiology
Decision Making - physiology
Dominance, Cerebral - physiology
Female
Frontal Lobe - physiology
Humans
Image Processing, Computer-Assisted

Judgment
Magnetic Resonance Imaging
Male
Paired-Associate Learning - physiology
Reaction Time - physiology
Reading
Semantics
Speech Perception - physiology
Temporal Lobe - physiology

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