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Global enhancement of task‐irrelevant dimensions of attended objects

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Title: Global enhancement of task‐irrelevant dimensions of attended objects
Author(s): Lustig, Audrey G.
Advisor(s): Beck, Diane M.
Contributor(s): Fabiani, Monica
Department / Program: Psychology
Discipline: Psychology
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: M.A.
Genre: Thesis
Subject(s): feature-based attention object-based attention Functional magnetic resonance imaging (fMRI)
Abstract: Experiments on the neural mechanisms of feature-based attention suggest that features are selected in parallel across the visual field (Treue & Trujillo, 1999). Moreover, feature-based attention spreads not only to the task-relevant feature in an unattended location, but also to a task-irrelevant feature when it is bound to the task-relevant feature in a task-irrelevant location (Sohn et al., 2005). We asked whether a similar mechanism is at work when the task-irrelevant feature is bound to the task-relevant feature at the attended location. Specifically, we asked whether attending to the color of moving dots in one visual field (VF) would influence the motion signal to colored moving dots in the other VF. Subjects attended to either red or cyan dots (both present in the upper right quadrant of the VF at the attended location and moving in opposite directions) and responded when the target dots dimmed. Critically, the color and motion of dots present in the upper left quadrant of the VF varied as a function of the attended dots such that they were either the same color/same direction, same color/opposite direction, opposite color/same direction, or opposite color/opposite direction as the attended dots. We found main effects of both color and direction in areas of ventral visual cortex responsive to the task-irrelevant location, such that BOLD activity was greater when either the dots’ color or direction were the same as the attended stimulus. We also found a main effect of direction in human MT/MST responsive to the task-irrelevant location, such that activity was greater when the dots in the task-irrelevant and task-relevant locations were moving in the same direction than when they were moving in opposite directions. These results support the theory that object-based attention leads to enhanced selection of all dimensions of the attended object, including task-irrelevant ones. Additionally, our findings suggest that this co-selection modulates the object’s dimensions independently throughout the visual field via a feature-based mechanism.
Issue Date: 2011-08-25
URI: http://hdl.handle.net/2142/26077
Rights Information: Copyright 2011 Audrey Lustig
Date Available in IDEALS: 2011-08-25
Date Deposited: 2011-08
 

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