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| Research article summary (published 29 Sep 2002): |
Separating relational from item load effects in paired recognition: temporoparietal and middle frontal gyral activity with increased associates, but not items during encoding and retention.
Full Abstract
Working memory is affected by items stored and the relations between them. However, separating these factors has been difficult, because increased items usually accompany increased associations/relations. Hence, some have argued, relational effects are reducible to item effects. We overcome this problem by manipulating index length:
the fewest number of item positions at which there is a unique item, or tuple of items (if length >1), for every instance in the relational (memory) set. Longer indexes imply greater similarity (number of shared items) between instances and higher load on encoding processes. Subjects were given lists of study pairs and asked to make a recognition judgement. The number of unique items and index length in the three list conditions were:
(1) AB,
CD:
four/one; (2) AB, CD,
EF:
six/one; and (3) AB, AD,
CB:
four/two, respectively. Japanese letters were used in Experiments 1 (kanji-ideograms) and 2 (hiragana-phonograms); numbers in Experiment 3; and shapes generated from Fourier descriptors in Experiment 4. Across all materials, right dominant temporoparietal and middle frontal gyral activity was found with increased index length, but not items during study. In Experiment 5, a longer delay was used to isolate retention effects in the absence of visual stimuli. Increased left hemispheric activity was observed in the precuneus, middle frontal gyrus, and superior temporal gyrus with increased index length for the delay period. These results show that relational load is not reducible to item load.
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Author information
Author/s: Phillips, Steven (S); Niki, Kazuhisa (K);
Affiliation: Neuroscience Research Institute, AIST, Tsukuba Central 2, Tsukuba, Ibaraki 305-8568, Japan. steve@ni.aist.go.jp
Journal and publication information
Publication Type: Clinical Trial; Journal Article
Journal: NeuroImage (Neuroimage), published in United States. (Language: eng)
Reference: 2002-Oct; vol 17 (issue 2) : pp 1031-55
Dates: Created 2002/10/14; Completed 2002/11/25; Revised 2004/11/17;
PMID: 12377177, 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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