The perception of curvature can be selectively disrupted in prosopagnosia

A brain-damaged patient with prosopagnosia and a group of age- and education-matched control subjects evaluated curved and straight versions of different sorts of stimuli in different tasks. The patient consistently required more time to encode curved than straight stimuli, relative to the control subjects. Specifically, he had a deficit when he compared curved lines that were simultaneously visible, when he compared curved lines with those previously seen, when he examined a curved shape to determine whether an X was on or off the shape, and when he read curved script. He also made more errors when he named pictures of curved objects. Implications of these findings for some types of clinical disorders and for the role of "end-stopped" cells in visual cortex are discussed.