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Abstract:
Detection of a target presented in a previously cued
location/object is slower compared to an uncued target. This is
termed Inhibition of Return (IOR; Posner & Cohen, 1984).
Initially, IOR was thought to be mediated solely by a
location-based representation and the product of midbrain
oculomotor structures, as evidenced by temporal/nasal hemifield
asymmetries under monocular viewing conditions (Rafal et al, 1988).
However, it is now clear that IOR can be the product of inhibition
mediated by both location- and object-based representations (Jordan
& Tipper, 1998a) and a recent study suggested that the
object-based effect relies on a cortical locus (Tipper et al,
1997). The Kanizsa illusion was exploited to observe
object+location- and location-based IOR effects in identical static
displays (Jordan & Tipper, 1998b) under monocular conditions.
It was predicted that a temporal/nasal asymmetry would be observed
in the location- and possibly a right/left hemifield asymmetry in
the object-based IOR effect (Egly et al, 1989). We found no
evidence of any asymmetry in the location-based inhibitory effect.
We did observe an exclusively left visual field benefit in the
object+location-based IOR effect which is consistent with a
previous report. Inhibitory object-based effects are the products
of right (not left) hemisphere representations. Although the
physiological basis for this object-based asymmetry remains
unclear, it differs from non-inhibitory attentional effects. These
observations suggest a cortical locus for both IOR effects.
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