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    Selective manipulation of target identification demands in visual search: the role of stimulus contrast in CDA activations

    Tollner, T. and Conci, M. and Rusch, T. and Muller, Hermann J. (2013) Selective manipulation of target identification demands in visual search: the role of stimulus contrast in CDA activations. Journal of Vision 13 (23), ISSN 1534-7362.

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    Abstract

    In classic visual pop-out search, response times are slowed remarkably when participants are required to precisely identify (e.g., vertical vs. horizontal orientation) as compared to simply localize (e.g., left vs. right position) a feature singleton target. This cost associated with stimulus identification has been recently proposed (Töllner, Rangelov, & Müller, 2012) to derive from the engagement of postselective recurrent processes that via feedback connections extract the information required for motor-response selection. Here, we examined whether the contralateral delay activity (CDA), an asymmetric neural marker generally assumed to reflect active maintenance of stimulus information in visual short-term memory (vSTM), may further index the degree of postselective processing requirements in visual search. Employing a compound-search task, we selectively manipulated the ease/difficulty of identifying the response-critical target orientation attribute (horizontal vs. vertical)—irrespective of the target-defining color feature (red vs. green)—by introducing different levels of stimulus-background contrast. As expected, we found a monotonic reaction time increase to be associated with gradually increasing CDA magnitudes as the stimulus contrast decreased. Thus, our findings provide direct evidence that CDA activations provide a useful tool to estimate the amount of postselective recurrent processing recruited to extract detailed object information from vSTM.

    Metadata

    Item Type: Article
    School: School of Science > Psychological Sciences
    Depositing User: Sarah Hall
    Date Deposited: 27 Oct 2015 12:04
    Last Modified: 27 Oct 2015 12:04
    URI: https://eprints.bbk.ac.uk/id/eprint/13194

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