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Kenneth Valyear, David Westwood, Nadder Sherif, Jonathan S. Cant, Melvyn A. Goodale; Differential fMRI adaptation for object identity and orientation in the ventral and dorsal streams.. Journal of Vision 2004;4(8):513. doi: 10.1167/4.8.513.
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We used an event-related fMRI adaptation paradigm to investigate changes in BOLD activity in the dorsal and ventral visual streams as a function of object identity and object orientation. On the basis of earlier work (James et al), we expected that areas in the dorsal stream would show sensitivity to changes in object orientation independent of object form whereas areas in the ventral stream would show sensitivity to changes in object form independent of object orientation. Participants (N=7) were presented with successive paired images of real-world, graspable objects, separated by a brief visual mask. The second image of each pair was either: i) identical in form and orientation to the first image, ii) identical in form but different in orientation iii) different in form but identical in orientation, or iv) different in both form and orientation. We identified distinct regions in the posterior cerebral cortex that were differentially sensitive to changes in form and orientation. In the dorsal stream, an area within the cIPS, extending into the superior occipital gyrus, showed a selective increase in BOLD activity with changes in object orientation. This same region was insensitive to changes in object form. In the ventral stream, areas within the LOC showed a selective increase in activity with changes in object form but were insensitive to changes in orientation. The differential sensitivity to object orientation and object form in these regions is consistent with the division of labour between the two streams. The dorsal stream, which plays a critical role in the visual control of actions such as grasping, might be expected to have networks that are particularly sensitive to the orientation of a goal object independent of its identity. By the same token, the ventral stream, which mediates object recognition, should have networks that are sensitive to the identity of objects independent of their orientation.
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