June 2006
Volume 6, Issue 6
Vision Sciences Society Annual Meeting Abstract  |   June 2006
Effects of spatial and non-spatial attentional load on posterior parietal cortex
Author Affiliations
  • Won Mok Shim
    Harvard University
  • George A. Alvarez
    Masachusetts Institute of Technology
  • Timothy J. Vickery
    Harvard University
  • Yuhong Jiang
    Harvard University
Journal of Vision June 2006, Vol.6, 518. doi:https://doi.org/10.1167/6.6.518
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      Won Mok Shim, George A. Alvarez, Timothy J. Vickery, Yuhong Jiang; Effects of spatial and non-spatial attentional load on posterior parietal cortex. Journal of Vision 2006;6(6):518. https://doi.org/10.1167/6.6.518.

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

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Purpose: The capacity limitation of human attention is best exemplified in attentive tracking of moving objects: our tracking ability declines when more objects are tracked, or when each object moves at a faster speed. Previous behavioral studies showed a trade-off between the number of objects tracked and the speed of each object, suggesting that a single type of attention is loaded. Using fMRI we examined whether common or separate neural substrates underlie spatial and non-spatial load. Methods: We parametrically manipulated two types of attentional load using an attentive tracking task. A rotating pinwheel was presented at each of four visual quadrants simultaneously. Observers tracked the cued spoke of a pinwheel(s) with attention while maintaining central fixation. We manipulated spatial load by cuing observers to monitor 1 or 2 pinwheels, and non-spatial load by varying the rotation speed of each wheel. Results: Tracking accuracy deteriorated as each wheel rotated more rapidly, with a sharper decline when more wheels were tracked. Posterior parietal cortex, however, was sensitive only to spatial load. Its activation was higher when subjects tracked 2 rather than 1 wheel, but showed no systematic change at different rotation speeds (from 100–400deg/s). In addition, although tracking accuracy was higher in bilateral tracking than unilateral tracking of two wheels, posterior parietal activity was equivalent between these two conditions. Conclusion: These results suggest that spatial and non-spatial attentional load are represented differently in the brain, with the posterior parietal cortex more sensitive to spatial attentional load than to non-spatial attentional load.

Shim, W. M. Alvarez, G. A. Vickery, T. J. Jiang, Y. (2006). Effects of spatial and non-spatial attentional load on posterior parietal cortex [Abstract]. Journal of Vision, 6(6):518, 518a, http://journalofvision.org/6/6/518/, doi:10.1167/6.6.518. [CrossRef]
 This study was supported by ARO-46926LS and NSF 0345525

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