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Abstract:
Early neuropsychological observations described a patient that presented with impaired knowledge of object orientation but spared object recognition skills [1]. Similar cases exhibiting this peculiar dissociation have been reported since Best’s discovery. Interestingly, a recent study observed a double dissociation between object identification and orientation [2]. These findings were interpreted as evidence that separate cortical centers underlie visual object recognition and processing of spatial features. Accordingly, visual object perception has been suggested to follow two different routes in the human brain: a ventral, view-invariant occipital-temporal route
processes object identity, whereas a dorsal, view-dependent occipital-parietal route processes spatial properties of an object. Using fMRI, we addressed the question whether these routes are exclusively involved in either object recognition or representation of object orientation. To
this end, we presented subjects with images of natural objects and involved them either in an object identification or object orientation judgment task. For both tasks we observed activation in ventro-temporal as well as parietal areas bilaterally, with significantly stronger responses for the orientation judgment in ventro-temporal areas. Our findings suggest that object identification and orientation judgment do not follow strictly separable cortical pathways, but rather involve both the dorsal and the ventral stream.
