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Audrey G. Lustig, Diane M. Beck; Global modulation of task-relevant and task-irrelevant dimensions of attended objects. Journal of Vision 2011;11(11):138. doi: 10.1167/11.11.138.
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In a previous fMRI study, we showed that attending to multidimensional objects (i.e. containing color and direction of motion) enhances the neural response to features of the attended object across the visual field, both for task-relevant and task-irrelevant dimensions (Lustig & Beck, in preparation). These results support the integrated competition hypothesis, which proposes that attending to an object enhances relevant over irrelevant stimuli by biasing all neural systems toward the individual dimensions of the attended object, including task-irrelevant ones (e.g., Duncan & Humphreys, 1987). In the current experiment, we investigated whether there are behavioral consequences of global modulation of task-relevant and task-irrelevant dimensions of attended objects. Subjects attended to one of two overlapping multidimensional objects at center and monitored for transient changes in one dimension of the attended object. Occasionally, four items were briefly presented around the central stimulus (two items above fixation and two items below). Each item varied in the degree of similarity to the centrally attended object, either containing i) both task-relevant and task-irrelevant dimensions, ii) only the task-relevant dimension, iii) only the task-irrelevant dimension, or iv) neither the task-relevant nor the task-irrelevant dimensions. On every trial, one of the four peripheral items had a distinctive shape (target); subjects were instructed to locate this target item as quickly and as accurately as possible. Our results indicate that subjects were more accurate at locating the target item when the target contained the same versus the opposite color as the centrally attended stimulus, regardless of whether color was the task-relevant or task-irrelevant dimension. This finding supports the theory that object-based selection results in global enhancement of all dimensions belonging to the attended object and further suggests that this enhancement improves target detection.
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