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Abstract

The dissociation between object identity and object orientation recently observed in five
patients with brain damage, has been taken as evidence for a view-invariant model of
object recognition. However, there was also some indication that these patients were not
agnostic for object orientation but were able to gain access to at least some information
about objects' canonical upright. We studied a new case with spared knowledge of object
identity and impaired perception of object orientation using a forced choice paradigm to contrast directly the patient's ability to perceive objects' canonical upright vs. non-upright orientations. We presented 2D-pictures of objects with unambiguous canonical upright orientations in four different orientations (0°, -90°, +90°, 180°). KB showed no impairment
in identifying letters, objects, animals, or faces irrespective of their given orientation.
Also, her knowledge of upright orientation of stimuli was perfectly preserved. In
sharp contrast, KB was not able to judge the orientation when the stimuli were presented
in a non-upright orientation. The findings give further support for a distributed viewbased representation of objects in which neurons become tuned to the features present in certain views of an object. Since we see more upright than inverted animals and familiar
objects, the statistics of these images leads to a larger number of neurons tuned for
objects in an upright orientation. We suppose that for this reason KB’s knowledge of
upright orientation was found to be more robust against neuronal damage than knowledge of other orientations.