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Abstract:
We used event-related fMRI to investigate the functional
neuroanatomy of different processes in directing visual spatial
attention. For this purpose, we used noninformative peripheral cues
(brightening of one of two boxes 7.5° left and right of
fixation) followed by the target at an stimulus onset asynchrony
(SOA) of 100ms, respectively 500ms (Posner & Cohen, 1984). In
accord with the literature, valid cues exerted a facilitatory
effect on reaction time at SOA=100ms and an inhibitory effect
(inhibition of return, IOR) at SOA=500ms. Whereas directing at
SOA=100ms is considered to be a purely attentional phenomenon, IOR
is discussed to be a compound of at least partly independend
attentional and occulomotor processes. Analysis of functional data
revealed a significant interaction of cue validity (valid, invalid)
x SOA (100ms, 500ms) in left frontopolar cortex (FPC, BA 10), right
anterior middle frontal gyrus (MFG, BA 10), left posterior MFG (BA
9), right angular gyrus (AG, BA 19), right anterior superior
temporal sulcus (STS, BA 21), and left middle insula (BA 13).
Anterior MFG and STS showed signal increases with IOR, whereas less
insular activation with IOR was observed. Activity in FPC,
posterior MFG and AG increased with invalid cues at SOA=100ms. We
conclude that the redirection of attention to invalidly cued
targets and the process related to IOR are relying on different
neural systems.
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