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    Does contralateral delay activity reflect working memory storage or the current focus of spatial attention within visual working memory?

    Berggren, Nick and Eimer, Martin (2016) Does contralateral delay activity reflect working memory storage or the current focus of spatial attention within visual working memory? Journal of Cognitive Neuroscience 28 (12), pp. 2003-2020. ISSN 0898-929X.

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    Abstract

    During the retention of visual information in working memory, event-related brain potentials show a sustained negativity over posterior visual regions contralateral to the side where memorised stimuli were presented. This contralateral delay activity (CDA) is generally believed to be a neural marker of working memory storage. In two experiments, we contrasted this storage account of the CDA with the alternative hypothesis that the CDA reflects the current focus of spatial attention on a subset of memorized items set up during the most recent encoding episode. We employed a sequential loading procedure where participants memorised four task-relevant items that were presented in two successive memory displays (M1 and M2). In both experiments, CDA components were initially elicited contralateral to task-relevant items in M1. Critically, the CDA switched polarity when M2 displays appeared on the opposite side. In line with the attentional activation account, these reversed CDA components exclusively reflected the number of items that were encoded from M2 displays, irrespective of how many M1 items were already held in working memory. On trials where M1 and M2 displays were presented on the same side, and on trials where M2 displays appeared non-laterally, CDA components elicited in the interval after M2 remained sensitive to a residual trace of M1 items, indicating that some activation of previously stored items was maintained across encoding episodes. These results challenge the hypothesis that CDA amplitudes directly reflect the total number of stored objects, and suggest that the CDA is primarily sensitive to the activation of a subset of working memory representations within the current focus of spatial attention.

    Metadata

    Item Type: Article
    School: Birkbeck Schools and Departments > School of Science > Psychological Sciences
    Depositing User: Martin Eimer
    Date Deposited: 25 Aug 2016 07:48
    Last Modified: 02 Jun 2017 09:46
    URI: http://eprints.bbk.ac.uk/id/eprint/15731

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