September 2021
Volume 21, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2021
Can MEG Source Localization Reveal the Time Course of Processing in the FFA, PPA, and EBA?
Author Affiliations & Notes
  • Kirsten Lydic
  • Dimitrios Pantazis
  • Nancy Kanwisher
  • Footnotes
    Acknowledgements  This work was supported by NIH grant Grant DP1HD091947 to NK and the National Science Foundation Science and Technology Center for Brains, Minds, and Machines
Journal of Vision September 2021, Vol.21, 2758. doi:
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      Kirsten Lydic, Dimitrios Pantazis, Nancy Kanwisher; Can MEG Source Localization Reveal the Time Course of Processing in the FFA, PPA, and EBA?. Journal of Vision 2021;21(9):2758.

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

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fMRI has provided a rich spatial map of category-selective responses across the ventral visual cortex, and EEG/MEG can inform the precise time course of visual processing. But what we really need is both temporal and spatial precision simultaneously. Can MEG source localization reveal the time course of processing in specific functional regions, distinguishing them from nearby regions? Here we addressed that question by collecting both MEG and fMRI responses from the same fifteen participants to the same images of faces, bodies, scenes, and objects. We used fMRI localizers to define the FFA, PPA, and EBA in each participant individually. We then computed source estimates from the MEG data using dynamic statistical parametric mapping, extracting the time courses of estimated MEG source amplitudes to each stimulus category within each fMRI-derived ROI. Source-localized MEG data showed a selective response to bodies peaking at about 160 ms in bilateral EBA that was not present in the FFA or PPA. A highly prominent right-lateralized face response peaking around 130 ms was detected in all three fROIs, while no clear peak response to scenes was present in any fROI. Analyses of source-localized responses across the whole cortex revealed a similar picture, with scene-selective responses spatially blurred across the occipital cortex, right-lateralized face-selective responses spanning much of the ventral surface of the cortex (extending well beyond the fusiform gyrus), and body-selective responses arising later on the lateral surface of both hemispheres in the vicinity of the EBA. These results suggest that right-lateralized face processing peaks on the ventral surface of the brain around 130 ms and body-selective processing on the lateral surface around 160 ms. However, they also indicate that MEG source localization is unable to detect fMRI-expected signals from some regions (PPA) or to precisely localize signals to the spatial grain of fMRI-defined functional regions.


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