Pei-Yin Chen^1,2, Atsushi Wada^1,2; ¹Center for Information and Neural Networks (CiNet), NICT, Osaka, Japan, ²Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan

Polar angle asymmetries in the cortical organization of human V1 have been previously revealed by fMRI retinotopic measurements in central vision. Building on our previous work, which demonstrated that population receptive field (pRF) analysis can be used to effectively characterize retinotopic organization across both central and far-peripheral vision, this study investigates polar angle asymmetries in the far-peripheral visual cortex. Specifically, we examined how pRF parameters vary with cortical distance along horizontal and vertical meridians in areas V1 to V3. Seventeen participants viewed the retinotopic stimuli through a wide-view binocular visual stimulation system in the MRI scanner, which allowed the visual presentation to cover approximately 90 degrees of the visual field. We applied a 2D Gaussian pRF model to the BOLD activations of voxels in areas V1 to V3 to estimate the pRF profiles. Our data show that pRF eccentricity generally increased with cortical distance from the visual center. However, this increase occurred more rapidly along the horizontal meridian compared to the vertical meridian in area V1, especially in far peripheral visual field. This asymmetry may be related to the difference in horizontal and vertical extent of the visual field due to the presence of monocular region. Additionally, pRF size also increased with cortical distance and then reached a saturation point, but the saturation occurs at a larger value for the horizontal meridian compared to the vertical meridian. Interestingly, these polar angle asymmetries in pRF eccentricity and pRF size were not observed in areas V2 and V3.

Acknowledgements: JSPS KAKENHI (Japan) 24K16880, 19K12745