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Lawrence Appelbaum, Wen Chen, Karen Meyerhoff, Lauren Davis, Robert Won, Marty Woldorff; Priming and backward interference in the human brain: SOA manipulations reveal processing interactions during the Stroop and reverse Stroop tasks. Journal of Vision 2009;9(8):85. doi: 10.1167/9.8.85.
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© ARVO (1962-2015); The Authors (2016-present)
In the present study, we exploit the high temporal resolution of EEG to study processing interactions in the human brain using variants of the Stroop (color naming) and Reverse Stroop (word naming) tasks in which the task-relevant and -irrelevant features were presented with varying temporal separations. High-density event-related potentials (ERPs) and behavioral performance were measured while participants reported in separate experimental session, either the bar color or the color-word, as quickly as possible while ignoring the other dimension. The task-irrelevant component could appear at one of five stimulus onset asynchronies (SOAs) relative to the presentation of the task-relevant component: −200 or −100 ms before, +100 or +200 ms after, or simultaneously. ERP and behavioral markers of stimulus conflict (congruent vs. neutral vs. incongruent) and of target selection (word vs. color) are considered.
We observed for both tasks that incongruent relative to congruent presentations elicited slower reaction times, higher error rates, and characteristic ERP difference waves. Responses for the two tasks both contained early, negative-polarity, central-parietal deflections, and later positive components, though the distribution and latencies differed slightly with task. These congruency-related differences interacted with SOA, showing the greatest behavioral and electrophysiological effects when irrelevant stimulus information preceded task-relevant target occurrence and reduced effects when the irrelevant information followed the relevant target. We interpret these data as reflecting two separate processes: (1) a priming mechanism for the more efficient processing of a task-relevant target stimulus when preceded by a congruent, but irrelevant distractor; and (2) the diminishing effects of Stroop-related interference when irrelevant distractor information follows the task-relevant target. The high-degree of symmetry in the timing of these effects for these two tasks suggests that stimulus incongruency affects the strength, rather than the speed, of processing in the activated brain network.
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