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Abstract:
"Inhibition of return" (IOR) refers to a slowing in responses
to a target presented at a previously cued/attended location at
long cue target delays. IOR is thought to facilitate search by
creating a bias to inspect novel locations. Although the superior
colliculus (SC) seems critical for the expression of IOR, Dorris et
al. (1998) found that neurons in the SC are not directly inhibited
or suppressed when IOR occurs, suggesting that other brain regions
might modulate IOR effects. The parietal cortex is one such
candidate region given its role in attentional orienting, spatial
working memory, and its rich interconnections with the SC. We
investigated the role of the parietal cortex in IOR by testing JB.
a patient with right posterior parietal damage. While there was no
difference in JB's ability to detect individual targets in either
hemifield, at a 750 msec cue-target delay, her IOR effect was
diminished contralesionally. Two explanations for this diminished
IOR effect can be postulated. The contralesional inhibition might
be dampened generally or, the inhibition might take longer to build
up contralesionally. Further testing using cue -target delays
varying from 750 to 1500 msec, suggested that the diminished IOR
effect was due to a general dampening, rather than a delay in the
build up of contralesional inhibition.
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