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Peter U. Tse, Gideon P. Caplovitz; V3A processes contour curvature as a trackable feature for the perception of rotational motion. Journal of Vision 2006;6(6):578. doi: 10.1167/6.6.578.
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© ARVO (1962-2015); The Authors (2016-present)
In a remarkable set of visual illusions, an object appears to change the angular velocity of its rotation as its shape changes. We (Caplovitz et al, VSS 2004, SFN 2005) have argued that contour curvature (CC) is a vital cue for the analysis of both form and motion that underlies this effect. Using fMRI, we localized the neural correlates of CC for the processing and perception of rotational motion. We found that the blood oxygen level dependent (BOLD) signal in retinotopic area V3A varied parametrically with the degree of CC. Control experiments ruled out the possibility that these modulations resulted from changes in the area of the stimuli, the velocity with which contour elements were translating, and perceived angular velocity. Based on the results of these experiments, we conclude that neuronal processing in area V3A serves to analyze CC as a trackable feature for the perception of rotational motion, and that this form-based feature is used to determine the speed and direction of motion. This raises the possibility that V3A functions in part as an area that processes form, not to solve the ‘ventral problem’ of determining object shape, but in order to solve the ‘dorsal problem’ of what is going where. We predict that this area will respond to the continuous motion of other contour discontinuities as well, such as junctions, corners, and terminators.
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