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Abstract:
Abstract: Many studies on visual object recognition have
sought to assign autonomous functions to the dorsal and ventral
cortical systems. However, we present evidence suggesting that
visual object recognition emerges from collaboration between the
dorsal (parietal) and ventral (inferior-temporal) systems. Using
3.0T functional magnetic resonance imaging (fMRI) we monitored the
amount and time-course of activation in the two cortical systems
while participants identified line drawings of common objects. In a
first experiment, the amount of available shape in the line
drawings was manipulated by deleting varying levels of contour. In
a second experiment, the orientation of presented objects was
manipulated by presenting drawings in a normal upright orientation,
or rotated in the picture plane. The conditions in which more
contour was deleted or in which objects were rotated were expected
to impose more visual demand and hence result in greater activation
in task-relevant areas. We observed increased activation in both
the dorsal and ventral systems with increases in each type of
demand. Furthermore, the times courses of voxels in the two systems
were highly correlated, indicating that the activity of both
systems was highly synchronized. The responses of both cortical
systems and the degree of their collaboration provide a contrast to
hypotheses that associate visual recognition exclusively with the
ventral cortical system.
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