October 2020
Volume 20, Issue 11
Open Access
Vision Sciences Society Annual Meeting Abstract  |   October 2020
What is the role of working memory in hybrid search?: Evidence from the Contralateral Delay Activity
Author Affiliations & Notes
  • Lauren Williams
    University of Utah
  • Iris Wiegand
    Brigham and Womens Hospital, Harvard University
    Max Planck UCL Centre for Computational Psychiatry and Ageing Research
  • Mark Lavelle
    University of Utah
  • Jeremy Wolfe
    Brigham and Womens Hospital, Harvard University
  • Keisuke Fukuda
    University of Toronto Mississauga
  • Trafton Drew
    University of Utah
  • Footnotes
    Acknowledgements  The National Science Foundation Graduate Research Fellowship Program (Grant #1747505) awarded to LW. Binational Science Foundation (Grant #2015301) awarded to TD.
Journal of Vision October 2020, Vol.20, 261. doi:https://doi.org/10.1167/jov.20.11.261
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      Lauren Williams, Iris Wiegand, Mark Lavelle, Jeremy Wolfe, Keisuke Fukuda, Trafton Drew; What is the role of working memory in hybrid search?: Evidence from the Contralateral Delay Activity. Journal of Vision 2020;20(11):261. https://doi.org/10.1167/jov.20.11.261.

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      © ARVO (1962-2015); The Authors (2016-present)

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In “Hybrid Search”, observers search for any member of a set of targets held in memory. Current hybrid search models propose working memory (WM) serves to pass representations of attended items one at a time from early visual processes into long-term memory (LTM) for comparison to target representations (Drew, et al., 2015). Here, we sought to better understand the role of WM in hybrid search using an ERP component associated with WM load, the Contralateral Delay Activity (CDA). Participants (N=20) memorized setsizes (MSS) of 2 or 16 categorical targets (dogs, cats, tables, or dressers), counterbalanced across participants. Next, they passed a recognition memory test twice with >=80% accuracy. Then, for 700 trials (per MSS), participants were cued to attend to one lateralized search item and indicate if a target was present. The cued object was either a target (e.g., target cat), a non-target from the target category (e.g., non-target cat), a non-target from a similar category (e.g., dog), or a non-target from a dissimilar category (e.g., table). ERP waveforms were time-locked to search onset. Overall, CDA amplitude was larger for objects from the target category, which provides support for the idea that processing is terminated for irrelevant objects following initial object identification (Cunningham & Wolfe, 2014). For objects within the target category, CDA amplitude increased with MSS, suggesting LTM load-dependent WM involvement in hybrid search. Furthermore, N2pc amplitude increased as the non-targets became more similar to the object category, but only for MSS16. This suggests more non-targets with similar features were selected for further processing in memory at larger MSS. Together, these findings demonstrate WM plays a larger role in hybrid search than previously thought. Specifically, to identify objects within the target category, WM resources may be deployed to compare the target set held in LTM to the potential target.


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