Fig. 6: A mismatch in bias and co-variations in the inter-individual difference between the pRF anisotropy and the perceptual anisotropy.

a Across-individual averages of the radial bias indices of the pRF (\({{RI}}_{{{{{{\rm{pRF}}}}}}}\)) and perceptual (\({{RI}}_{{{{{{\rm{perc}}}}}}}\)) anisotropies in the radial and tangential orientation conditions. The x-axis values of the symbols are the across-individual averages of \({{RI}}_{{{{{{\rm{pRF}}}}}}}\) for V1, V2, and V3. As for the y-axis values, the one and same across-individual average of \({{RI}}_{{{{{{\rm{perc}}}}}}}\) is repeatedly used for the symbols in each stimulus orientation condition. The solid horizontal bars are the across-individual and across-area averages of \({{RI}}_{{{{{{\rm{pRF}}}}}}}\) values for the radial (orange) and tangential (blue) orientation conditions. The empty vertical bars are the across-individual averages of \({{CI}}_{{{{{{\rm{perc}}}}}}}\) values for the two orientation conditions. Note that the average value of \({{CI}}_{{{{{{\rm{perc}}}}}}}\) in the tangential orientation condition was converted from that of \({{RI}}_{{{{{{\rm{perc}}}}}}}\) by flipping the sign (as defined in the bottom panel of c). Dots, 27 observers; Symbols and error bars, mean and 95% CI; Upward triangle, square, downward triangle, and crosshair symbols represent V1, V2, V3, and the average of V1-3. b Across-individual co-variations between the influences of radiality on the pRF and perceptual anisotropies, shown separately for the radial (orange) and tangential (blue) orientation conditions. For each orientation condition, the \({{RI}}_{{{{{{\rm{perc}}}}}}}\) values of 27 individuals are plotted against the averages of their \({{RI}}_{{{{{{\rm{pRF}}}}}}}\) values across the visual areas. In both conditions, the \({{RI}}_{{{{{{\rm{perc}}}}}}}\) values were significantly regressed onto the \({{RI}}_{{{{{{\rm{pRF}}}}}}}\) values, as depicted by the linear regression lines and Pearson correlation values. c Definition of the co-axial modulation index of pRF anisotropy (\({{CMI}}_{{{{{{\rm{pRF}}}}}}}\)) and the mean co-axial bias index of perceptual anisotropy (\({\overline{{CI}}}_{{{{{{\rm{perc}}}}}}}\)). Top, \({{CMI}}_{{{{{{\rm{pRF}}}}}}}\) quantifies the modulatory influence of co-axiality on the pRF anisotropy based on the difference between the \({{RI}}_{{{{{{\rm{pRF}}}}}}}\) values of the two orientation conditions. Bottom, \({\overline{{CI}}}_{{{{{{\rm{perc}}}}}}}\) quantifies the mean degree of the co-axial bias in the perceptual anisotropy by averaging the \({{CI}}_{{{{{{\rm{perc}}}}}}}\) values of the two orientation conditions, which were converted from the corresponding values of \({{RI}}_{{{{{{\rm{perc}}}}}}}\). d Across-individual co-variations between the influences of co-axiality on the pRF and perceptual anisotropies. The \({\overline{{CI}}}_{{{{{{\rm{perc}}}}}}}\) values of 27 individuals are plotted against the averages of their \({{CMI}}_{{{{{{\rm{pRF}}}}}}}\) values across the visual areas. The \({\overline{{CI}}}_{{{{{{\rm{perc}}}}}}}\) values were significantly regressed onto the \({{CMI}}_{{{{{{\rm{pRF}}}}}}}\) values, as depicted by linear regression line and Pearson correlation value. a, b, d Schematically depicted ellipsoids are used as guides on the x and y axes to visually illustrate the topographic anisotropies corresponding to the \({{RI}}_{{{{{{\rm{pRF}}}}}}}\) and \({{RI}}_{{{{{{\rm{perc}}}}}}}\) values (a, b) or the \({\overline{{CI}}}_{{{{{{\rm{perc}}}}}}}\) and the \({{CMI}}_{{{{{{\rm{pRF}}}}}}}\) values (d).