Group-averaged cortical map of curvature-preferring regions projected onto the freesurfer averaged inflated brain (top) and a flattened brain (bottom). The map was generated by contrasting fMRI responses to curvilinear (round shapes and computer-generated 3D sphere array) > rectilinear (rectilinear shapes and computer-generated 3D pyramid array) stimuli, the same contrast as in Fig. 3. Red/yellow activation indicates curvature response preference, and blue/cyan activation indicates rectilinear response preference. The dotted white lines shown on the flattened brain (bottom) indicate the retinotopic boundaries between early visual areas identified by the retinotopic mapping runs. Black lines indicate the boundary of OCP and solid white lines indicate the boundary of FCP. The blue outline shows the boundary of the occipital face area (OFA) and green lines show the boundaries of the fusiform face area (FFA) and anterior temporal face area (ATFA). The right OCP completely overlapped the right OFA and bilateral FCP partially overlapped FFA in both hemispheres (see Section 3.3 for quantification). Scene-selective areas were defined by fMRI responses to scenes > curvilinear and rectilinear stimuli. Yellow lines indicate the boundary of the parahippocampal place area (PPA) and dotted yellow lines outline retrosplenial cortex. The rectilinear-preferring patch overlapped PPA bilaterally (see Section 3.3 for quantification). The corrected statistical threshold was FDR
Comparison of group-averaged cortical maps of regions with significant curvature response preference across stimulus type (conditions 1 and 2 vs. conditions 3 and 4). Group-averaged maps were projected onto the FreeSurfer averaged flattened brain. The map on the top was generated using the fMRI activity contrast of round > rectilinear real-world objects. The map on the bottom was generated using the fMRI activity contrast of computer-generated 3D sphere array > computer-generated 3D pyramid array. Yellow/red activation indicates the curvature response preference; blue/cyan indicates the rectilinear response preference. Black outlines indicate the boundaries of the curvature-preferring patches. As expected, because the image size of the computer-generated stimuli was larger than that of the real-world objects, we observed more early visual areas activated by the computer-generated stimuli (top) than real-world objects (bottom). However, all curvature-preferring regions observed in the combined map (Fig. 4) are present in the separated maps, indicating the consistency of curvature preference regions across stimulus type. The corrected statistical threshold was FDR
Fig. 6.
Correlation of fMRI activity with…
Fig. 6.
Correlation of fMRI activity with curvilinear values in curvature-preferring patches was significant in…
Fig. 6. Correlation of fMRI activity with curvilinear values in curvature-preferring patches was significant in left V3dCP (r = 0.763, p = 0.028), left V3vCP (r = 0.729, p = 0.040), and left V4CP (r = 0.866, p = 0.005), but not in right V3dCP/ V3vCP, V4CP (data not shown), or bilateral higher level curvature patches (OCP, FCP, see Fig. S2). All error bars represent the S.E.M. Significant correlations observed for left V3dCP, left V3vCP, and left V4CP suggest that these responses in curvature-preferring patches relate to simple curvilinear information. We did not observe significant correlations between the rectilinear values of the stimuli and fMRI responses in any of the curvature patches (Fig. S3).
Fig. 7.
Correlation of the predicted fMRI…
Fig. 7.
Correlation of the predicted fMRI response from the linear combination of curvature values…
Fig. 7. Correlation of the predicted fMRI response from the linear combination of curvature values with fMRI activity in OCP and FCP. The correlation is significant in left and in right OCP (left OCP, r = 0.885, p = 0.002; right OCP, r = 0.702; p = 0.029), but not in left and right FCP (left FCP, r = 0.444, p = 0.129; right FCP, r = 0.342, p = 0.214), suggesting that OCP plays a role in processing complex curvilinear information derived from simple curvilinear information (such as curved lines).
Fig. 8.
Group PCA map. (top) Inflated…
Fig. 8.
Group PCA map. (top) Inflated view of the ventral surface. Areas outlined in…
Fig. 8. Group PCA map. (top) Inflated view of the ventral surface. Areas outlined in black on the inflated brain indicate the location of the mid-fusiform sulcus. Visual areas in red/yellow were associated with positive values of the second principal component (PC2) while those in blue/cyan were associated with negative PC2 values. (bottom) Flattened view of the ventral surface. The visual cortex associated with the positive PC2 values included OCP (black outline), FCP (white outline), OFA (blue outline), FFA (green outline); the visual cortex associated with the negative PC2 values encompassed PPA (yellow outline) and rectilinear-preferring areas (not outlined, see Fig. 4). The absolute values of PC2 are not meaningful, because the data were normalized in the PCA analysis. Given that the loading of PC2 correlated significantly with the curvilinear values of visual stimuli across conditions (Fig. S5: r = 0.85, p = 0.007; permutation test: see Methods), the areas in red/yellow might be involved in processing curvilinear features and those in blue/cyan might be implicated in processing rectilinear features. The dashed white line indicates the central-peripheral boundary in our stimuli defined by contrasting the fMRI response to computer-generated 3D spheres and pyramid arrays (20 × 15˚) vs. faces and objects (8.4 × 10.0˚). Local orientations of the brain axes on the flattened brain are indicated in white letters (D = dorsal; V = ventral; P = posterior; A = anterior).
Fig. 9.
Individual subject PCA maps. Each…
Fig. 9.
Individual subject PCA maps. Each subject’s data ( N = 15) were projected…
Fig. 9. Individual subject PCA maps. Each subject’s data (N = 15) were projected onto their native flattened surface. Relatively consistent across all subjects, the visual cortex associated with positive PC2 values was confined within the central visual field in the early visual areas, and then extended continuously to the anterior temporal lobe through lateral occipitotemporal areas. Regions of visual cortex associated with negative PC2 values extended from peripheral visual field representations in early visual areas to the medial surface of the occipitotemporal cortex and then to the collateral sulcus (CoS) and parahippocampal gyrus. The dashed white line indicates the anatomical border between the fusiform gyrus and the collateral sulcus. Local orientation of the brain axes on the flattened brain are indicated in white letter (D = dorsal; V = ventral; P = posterior; A = anterior).