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Carmel Mevorach, Lilach Shalevl; Impaired saliency suppression in old age: left IPS indifference lets extrastriate cortex run wild. Journal of Vision 2014;14(10):630. doi: 10.1167/14.10.630.
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Top-down attention selection may involve both target enhancement and distractor suppression. These mechanisms, however, appear to be differentially affected in ageing. In particular it has been argued that distractor suppression is impaired as we age (Gazzaley et al., 2005). In accordance with this concept we have previously shown (Tsevetanov et al., 2013) that older participants are particularly impaired at ignoring salient distracters when instructed to respond to low salient targets. We have also shown that in young adults this function relies on a parieto-occipital circuit whereby left IPS down-regulates cortical responses to salient distracters in visual cortex (Mevorach et al., 2010). Here we investigate the underlying brain circuitry that accompanies reduced salience-suppression in old age by inspecting the brain network typically involved in such top-down selection. We used fMRI with old and young adults who were asked to identify either the global or the local aspect of a hierarchical letter under conditions where the target or the distractor level is more salient. Behaviourally, old adults showed increased susceptibility to salient distracters on both the global and local levels. Furthermore, left IPS recruitment in distractor-salient conditions was absent in the older group. At the same time there was also evidence that in old (but not in young) participants specialised extrastriate visual cortex regions are driven primarily by the bottom-up saliency of the global and local information. The data suggest that impaired top-down attention in old age is associated with an indifferent attention control which in turn lets the visual representation be dominated by bottom-up saliency. An open question remains as to whether this is the manifestation of impairment in the top-down mechanism or rather simply a change in strategy where suppression is not called upon (but is not otherwise impaired).
Meeting abstract presented at VSS 2014
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