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Carmel Mevorach, Harriet Allen, John Hodsoll, Lilach Shalev, Glyn Humphreys; Interactivity between the left intraparietal sulcus and occipital cortex in ignoring salient distractors: Evidence from neuropsychological fMRI. Journal of Vision 2010;10(7):89. doi: 10.1167/10.7.89.
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© ARVO (1962-2015); The Authors (2016-present)
Visual attention mechanisms in the human brain act both to enhance the processing of relevant targets and to suppress the processing of irrelevant distractors. Attentional control mechanisms are typically linked to activity in a fronto-parietal network, but their effect can be measured in extrastriate visual cortex. Previous work indicates that the left intraparietal sulcus (IPS) is particularly critical for the selection of low saliency targets in the presence of higher-saliency distractors. Here we use neuropsychological fMRI to examine how interactions between the left IPS and extrastriate cortex generate selection by saliency. We compared activation patterns in the left IPS and in extrastriate visual cortex for responses to the local and global properties of compound letters. We tested two patients exhibiting distinct patterns of damage to extrastriate visual cortex which differentially affected their ability to select targets at local and global level. In healthy controls there was increased activity in the left IPS, but reduced activity in extra-striate visual cortex, when the target had low saliency and the distractor high saliency. Similar effects were found with the patients but only when distractors at their spared level of processing had high saliency. In contrast, there was increased activation in their intact extra-striate region when the target on their spared level of processing had low saliency. We conclude that the left IPS acts to bias the competition for selection against salient distracting information (rather than in favour of the low-salient target). In addition, in the absence of competition from salient distractors, extra-striate activity reflects target selection. We discuss the implications for understanding the network of regions controlling visual attention.
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