V3A processes contour curvature as a trackable feature for the perception of rotational motion.

Contour curvature (CC) is a vital cue for the analysis of both form and motion. Using functional magnetic resonance imaging, we localized the neural correlates of CC for the processing and perception of rotational motion. We found that the blood oxygen level-dependent signal in retinotopic area V3A and possibly also lateral occipital cortex (LOC) varied parametrically with the degree of CC. Control experiments ruled out the possibility that these modulations resulted from either changes in the area of the stimuli, the velocity with which contour elements were actually translating, or perceived angular velocity. We conclude that neurons within V3A and perhaps also LOC process continuously moving CC as a trackable feature. These data are consistent with the hypothesis that V3A contains neural populations that process trackable form features such as CC, not to solve the "ventral problem" of determining object shape but in order to solve the "dorsal problem" of what is going where.