Illustration from Scientific Research

Top: a stationary real-world edge segment (red line) may be locally approximated as a line of longitude or latitude. Center and bottom: the projection of a real-world edge follows lines of longitude or latitude on a hemispherical (center) and flattened (bottom) retina. The projection of similar-orientation edges at adjacent visual space locations (blue lines) aligns with local longitude or latitude lines. Asterisks, center of longitudinal (A, bottom) or latitudinal (B, bottom) fields. N, nasal; D, dorsal; T, temporal; and V, ventral.

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