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Thomas W. James, G. Keith Humphrey, Joseph S. Gati, Ravi S. Menon, Melvyn A. Goodale; Differing viewpoint effects in the ventral and dorsal visual streams revealed using fMRI. Journal of Vision 2002;2(7):45. doi: 10.1167/2.7.45.
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© ARVO (1962-2015); The Authors (2016-present)
Neuroimaging studies using object stimuli have typically focused on activation produced in the ventral occipital and temporal cortices, which are part of the ventral stream of visual processing. Many of these studies, however, also report activation in a region of the posterior parietal cortex, a part of the dorsal stream, that is activated by object stimuli. We investigated the contribution of this parietal region to object viewing, by using a priming paradigm in combination with high-field fMRI. Subjects were repeatedly presented with images of common and novel objects. Some of the repeated images were identical to the initial presentation and some of the images were of the same objects, but rotated in depth. We found that area LO, part of the ventral stream, showed viewpoint invariance, responding the same way to identical and rotated images of objects presented earlier. This result corresponded to behavioural data that showed equivalent performance with identical and rotated images. Area cIPS, part of the dorsal stream, showed priming only with identical images, and appeared to treat rotated images as new objects. This difference in the pattern of priming-related activation in the two areas may reflect the respective roles of the ventral and dorsal streams in object recognition and object-directed action. This difference may also reflect the use of object-based versus observer-based frames of reference in the ventral and dorsal streams.
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