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| Research article summary (published 30 Dec 2002): |
Nonconscious formation and reactivation of semantic associations by way of the medial temporal lobe.
Full Abstract
A successful strategy to memorize unrelated items is to associate them semantically. This learning method is typical for declarative memory and depends on the medial temporal lobe (MTL). Yet, only a small fraction of perceived items emerge into conscious awareness and receive the status of representations in declarative memory. This functional magnetic resonance imaging (fMRI) study tackled the mnemonic fate of unrelated item pairs processed without conscious awareness. Stimuli consisted of a face and a written profession (experimental condition) or of a face (control condition) exposed very briefly between pattern masks. Although the participants were unaware of the stimuli, activity in the hippocampus and perirhinal cortex was changed in the experimental versus the control condition; perirhinal activity changes correlated with the reaction time measure of the later nonconscious retrieval. For retrieval, the previously presented faces were shown again, this time for conscious inspection. The task was to guess the professional category of each face. This task was to induce a nonconscious retrieval of previously formed face-profession associations. Remarkably, activity in the hippocampus and perirhinal cortex was enhanced when subjects were confronted with faces from the experimental versus the control condition. The degree of hippocampal and perirhinal activation changes correlated with the reaction time measure of nonconscious retrieval. Together, our findings suggest that new semantic associations can be formed and retrieved by way of the medial temporal lobe without awareness of the associations or its components at encoding or any awareness that one is remembering at retrieval.
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Author information
Author/s: Henke, Katharina (K); Mondadori, Christian R A (CR); Treyer, Valerie (V); Nitsch, Roger M (RM); Buck, Alfred (A); Hock, Christoph (C);
Affiliation: Division of Psychiatry Research, Psychiatric University Hospital, University of Zürich, Lenggstrasse 31, 8029 Zürich, Switzerland. henke(-atsign-)bli.unizh.ch
Journal and publication information
Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't
Journal: Neuropsychologia (Neuropsychologia), published in England. (Language: eng)
Reference: 2003-; vol 41 (issue 8) : pp 863-76
Dates: Created 2003/04/01; Completed 2003/06/04; Revised 2006/11/15;
PMID: 12667523, 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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