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Andrew McCollough, Trafton Drew, Todd Horowitz, Edward Vogel; Probing the allocation of attention during multiple object tracking with ERPs. Journal of Vision 2008;8(6):222. doi: 10.1167/8.6.222.
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© ARVO (1962-2015); The Authors (2016-present)
While most researchers would agree that multiple object tracking (MOT) is an attentionally demanding task, the specific function of attention during tracking is not yet fully understood. For example, it is unclear whether attention during tracking enhances the target representations, suppresses the distractor representations, or some combination of excitation and inhibition of both the targets and distractors. Currently, there is some evidence that distractors are actively inhibited during tracking, but that there is no enhancement of targets relative to static space (Pylyshyn et al., 2006). These and other results generally rely upon dual task paradigms in which subjects attempt to detect the presence of an occasional probe on targets, distractors or space while they simultaneously perform the tracking task. However, the fact that the probes are task-relevant could be problematic because it may significantly alter how subjects allocate attention to the tracking task.
In the present study, we used ERPs to examine the early visual evoked responses to task-irrelevant probes while subjects performed a standard MOT task in which they tracked a near capacity load of four targets. This gave us a unique opportunity to examine the allocation of spatial attention during tracking without requiring an additional detection task. Brief probes were flashed on either targets, distractors, or stationary objects. The results showed a significant enhancement of the anterior N1 component (150ms) for probes on targets relative to distractors and stationary objects. Furthermore, this enhancement correlated with the subjects' tracking ability; Good trackers showed larger differences between target and nontarget probe responses than did poor trackers. These results provide evidence that attention enhances the representations of tracked target items.
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