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Abstract:
Patients with unilateral neglect who show object-centered
neglect typically ignore the left side of both objects and spaces.
The fact that spatial and object-centered attention are often
expressed in the same direction has led to debates about whether
spatial and object-centered attentional biases are the same or
different. One issue rarely considered is that the different tasks
used to assess performance with objects and environments may
differentially activate the two hemispheres. For instance, certain
right-hemisphere (RH) structures may be specialized for spatial
tasks and certain left-hemisphere (LH) structures may be
specialized for object tasks. We report extensive testing of a
patient, JM, with a right occipito-temporal lesion. JM was biased
to attend to the right side of objects, which would be expected
were performance on object tasks mediated primarily by the LH. At
the same time, he was biased to attend to the left side of spaces,
which would be expected were performance on spatial tasks primarily
mediated by the RH. Because JM's lesions interrupted fibers
coursing through the splenium of the corpus callosum, the
contralateral attentional bias of the hemisphere specialized for
these tasks was not opposed by the other hemisphere's tendency to
allocate attention in the opposite direction. We take these results
as evidence that object and spatial attentional biases are
different. Finally, we consider the extent to which task
requirements and attention can be distinguished.
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