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Abstract:
The neural substrate for attention has been postulated to
involve the posterior parietal lobe, thalamus, superior colliculus
(SC) and anterior structures such as cingulate and dorsolateral
prefrontal cortex (DLPFC). The facilitation & inhibition (IOR)
observed behaviourally when subject's respond to targets at
previously cued/uncued locations may involve different brain
structures, and a role for the SC in covert attentional orienting
has been suggested (e.g. Posner, 1990, Ann Rev. Neurosci. 13:25-42;
Rafal & Henik, 1994, in Carr & Dagenbach, Inhibitory
processes in attention. AP). In this study 6 subjects were imaged
(3.0T fMRI EPI/BOLD) during a tactile exogenous attentional
orienting experiment (Lloyd et. al., 1998, Somat. & Sen. Res.
in press) in which uninformative, and non predictive, vibratory
cues were delivered bilaterally to the feet, followed by targets
(SOA's of 200 or 700msec) at the cued or uncued locations. Stimuli
were randomised and RTs collected. Significant activation was
observed in SC, posterior parietal areas, M1, SMA, insular,
cingulate and DLPFC. Specific anatomical locations were activated
which correlated with the behavioural measures of either
facilitation or inhibition.
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