August 2023
Volume 23, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2023
Visually occluded grasp modulates orientation representation in human early visual cortex
Author Affiliations
  • Thanaphop Threethipthikoon
    Kochi University of Technology
  • Zhen Li
    University of Hong Kong
  • Hiroaki Shigemasu
    Kochi University of Technology
Journal of Vision August 2023, Vol.23, 5253. doi:
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      Thanaphop Threethipthikoon, Zhen Li, Hiroaki Shigemasu; Visually occluded grasp modulates orientation representation in human early visual cortex. Journal of Vision 2023;23(9):5253.

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

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Our previous fMRI study showed that even when visual information is occluded, orientation information of an object continues to be processed with the grasping action in the visual cortices of the human brain. However, it remains unknown to what extent the occluded action can influence the orientation representation in conjunction with the processes of action, such as haptics, proprioception, and action preparation. To investigate this point, the orientation representation in visual cortices was examined under four conditions: (1) observing an image of the orientation of a rod object and then grasping a real rod object, (2) observing the image and making a grasping action without an object, (3) observing the image and withholding the grasp, and (4) grasping an object without observing the image. The images of the rod object were shown with +45° or -45° orientations corresponding to those of the real object to be grasped with the whole-hand gesture. The participants judged the orientation in all condition. The grasping was performed without the online visual feedback of hand action and the object. Multivariate pattern analysis was used to examine the difference among the cortical patterns of four conditions during grasping or withholding grasp period. Overall, significant decoding accuracy over chance level was discovered for the condition 1, but in condition 2, only the early visual areas showed significant accuracy suggesting that haptic feedback of the object influences the orientation process in higher visual areas. The condition 3 showed no statistical significance in any area, indicating that without the grasping action, the orientation process was less effective. Interestingly, only the V3d showed significant decoding accuracy in the condition 4 despite the absence of visual orientation information of the object for grasping preparation, suggesting that the area V3d contains orientation representation derived from action processes without visual input.


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