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Abstract:
We present a neural model that can perform eye movements to a
particular side of an object 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 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, viz.,
without neurons whose receptive fields are 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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