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Marla Zinni, Antigona Martinez, Raja Parasuraman, Steven Hillyard; Attention spreads to unattended features of an object. Journal of Vision 2009;9(8):149. doi: 10.1167/9.8.149.
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There is increasing evidence that attention selects objects as integrated feature ensembles (O'Craven, Downing, & Kanwisher, 1999). However, little is known about the neural mechanisms that allow object features, often represented in dispersed cortical areas, to become bound together into a unified object percept. Schoenfeld et al., (2003) investigated this question using moving dot-arrays in which a task-irrelevant color feature would sometimes appear. That study demonstrated attentional selection of the color feature within 40 – 60 msec, in brain regions that represent color information, thus providing a potential mechanism for the binding of features across a multi-feature object. The present study was aimed at investigating whether the irrelevant color processing demonstrated in the Schoenfeld et al. study would generalize to a different type of object. Event-related potentials were recorded while subjects observed a grid of horizontal and vertical lines. During each block, participants were asked to attend to either the horizontal or vertical lines and to respond when a line of the attended orientation was thicker than usual. On two-thirds of the trials, vertical or horizontal lines were colored red instead of gray, and color was irrelevant to the task. Unattended red stimuli elicited a prominent sensory response beginning about 100 msec post stimulus onset relative to gray stimuli. Attentional selection of the task-irrelevant color feature (color on the attended orientation vs. color on the same orientation when unattended) occurred at about 300 msec, similar to the finding of Schoenfeld et al. (2003). These findings suggest that attention generally operates in an object-based manner and provides timing information for the binding of color to line orientation.
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