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Abstract:
We present a neural model that can perform eye movements to a
particular side of an object regardless of the position and
orientation of the object in space, a generalization of a task
which has been recently used by Olson and Gettner (Science, 269,
1995) to investigate the neural structure of object-centered
representations. Our model uses an intermediate representation in
which units have oculocentric receptive fields (just like
collicular neurons) whose gain is modulated by the side of the
object to which the movement is directed, as well as the
orientation of the object. We show that these gain modulations are
consistent with Olson and Gettner single cell recordings in the
supplementary eye field. This demonstrates that it is possible to
perform an object-centered task without a representation involving
an object-centered map, i.e., without neurons with receptive fields
defined in object-centered coordinates. We also show that the same
approach can account for object-centered neglect, a situation in
which patients with a right parietal lesion neglect the left side
of objects regardless of the orientation of the objects.
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