Fig. 8: High-dimensional topographic organization of the primate temporal lobe.

a Eigenvalues for principal components (PCs) of monkey feature maps. b Left: Procedures for half-split analyses (see Methods). Right: Solid lines indicate the average correlations of 500 iterations of half-splitting; dashed lines indicate the lower bounds of 1% confidence interval. c Projections of the 25D feature map onto the top three PCs (left), the top PCs’ positive and negative representative images (middle; note that the original ImageNet images are replaced with natural images from https://pixabay.com/), and cosine angles between the top three PCs and the 9 features in Figs. 3, 4 (right). d Spatial autocorrelations of the top six PCs for M1’s left hemisphere. e Autocorrelations within two orthogonal rectangles (left) were projected onto their long edges (middle). Fourier analyses were then performed on the projections (right). f By rotating the rectangles, the magnitude of Fourier transform was extracted for every angle and frequency, resulting in a polar plot for each PC. g Results for the left hemispheres of two other monkeys and the average of three monkeys for PC1 and PC2 of M1’s feature map, the same two dimensions as in (c–f). Triangles in the population-averaged graphs indicate preferred orientations for PC1’s low frequency and PC2’s high frequency. h Average results for the right hemispheres of three monkeys. The plots are flipped right to left to match the left hemisphere plots. i Magnitudes in the polar plots for PC1 (blue line) and PC2 (red line) are plotted against polar angles. For symmetry reasons, only angles in the range [−90^°, 90^°] were considered. Results for low and high frequencies are shown separately in the middle and on the right (low frequency=average of 1 and 2 cycs/6.6 cm, high frequency = average of 4 and 5 cycs/6.6 cm; see left). The two orthogonal orientations in panel e (arrows) roughly matched the tuning peak for PC1 at low frequency and that for PC2 at high frequency. Shadings represent SEM (n = 6 hemispheres). Insets: Peak magnitudes for PC1 and PC2 were compared (paired t-test, two-tailed, p = 0.001 and t(5) = 6.63 for low frequency, p = 9 × 10⁻⁴ and t(5) = −7.03 for high frequency, n = 6 hemispheres). Source data are provided as a Source Data file.