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Abstract:
The brain encodes visual features with respect to a frame of
reference. The reference frame specifies the center location, the
up-down, left-right, and front-back directions. Reference frames
can be prescribed by the viewer's gaze, intrinsic characteristics
of an object, or the environment. To determine the frames of
reference involved in human vision and attention, neurological
patients with unilateral neglect have been extensively studied.
Neglect patients often fail to orient toward, explore, and respond
to stimuli on the left. The interesting question is: with respect
of to what frame of reference is neglect of the left manifested?
When a neglect patient shows a deficit in attentional allocation
that depends not merely on the location of an object with respect
to the viewer but on the extent, shape, or movement of the object
itself, the inference is often made that attentional allocation
must be operating in an object-based frame of reference (Arguin
& Bub, 1993; Behrmann & Tipper, 1994; Pavlovskaya et al.,
1997; Driver et al., 1994; Tipper & Behrmann, 1996). Via
simulations of these and other data by a connectionist model of
spatial attention that operates entirely in an egocentric reference
frame, I argue that this inference is not logically necessary:
object-based attentional effects can be obtained without
object-based frames of reference.
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