Priming and Backward Influences in the Human Brain: Processing Interactions during the Stroop Interference Effect

Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA.
Cerebral Cortex (Impact Factor: 8.67). 04/2009; 19(11):2508-21. DOI: 10.1093/cercor/bhp036
Source: PubMed


This study investigated neural processing interactions during Stroop interference by varying the temporal separation of relevant and irrelevant features of congruent, neutral, and incongruent colored-bar/color-word stimulus components. High-density event-related potentials (ERPs) and behavioral performance were measured as participants reported the bar color as quickly as possible, while ignoring the color words. The task-irrelevant color words could appear at 1 of 5 stimulus onset asynchronies (SOAs) relative to the task-relevant bar-color occurrence: -200 or -100 ms before, +100 or +200 ms after, or simultaneously. Incongruent relative to congruent presentations elicited slower reaction times and higher error rates (with neutral in between), and ERP difference waves containing both an early, negative-polarity, central-parietal deflection, and a later, more left-sided, positive-polarity component. These congruency-related differences interacted with SOA, showing the greatest behavioral and electrophysiological effects when irrelevant stimulus information preceded the task-relevant target and reduced effects when the irrelevant information followed the relevant target. We interpret these data as reflecting 2 separate processes: 1) a 'priming influence' that enhances the magnitude of conflict-related facilitation and conflict-related interference when a task-relevant target is preceded by an irrelevant distractor; and 2) a reduced 'backward influence' of stimulus conflict when the irrelevant distractor information follows the task-relevant target.

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Available from: Lawrence Gregory Appelbaum, May 08, 2014
    • "Indeed, another limitation of the present study is that given the muscular and movement artifacts resulting from the use of the original vocal responses (Stroop, 1935), we were unable to explore some late components known to be sensitive to Stroop interference. Indeed, it would have been interesting to examine whether the late negativity (LN occurring 600–800 ms after stimulus onset; see, e.g., Hanslmayr et al., 2008) or the late positivity complex (LPC occurring between 500 and 900 ms; see, e.g., Appelbaum et al., 2009) are sensitive to the semantic and/or response conflict. Given that the detection and/or resolution of response conflict is thought to arise later in the processing of standard-incongruent Stroop words (e.g., Ferrand & Augustinova, 2014), it remains plausible that these late components are indeed sensitive to response conflict (see, e.g., Hanslmayr et al., 2008, for Strooprelated LN results that are compatible with such idea) and, thus, strongly modulated by SLC. "
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    ABSTRACT: By combining the semantic Stroop paradigm (e.g., Klein in American Journal of Psychology 77:576-588, 1964) with a single-letter coloring (SLC) procedure (e.g., Besner et al. in Psychonomic Bulletin & Review 4:221-225, 1997), this research investigated whether the frequently reported Stroop-related event-related potential (ERP) effect arising about 400 ms after stimulus onset (Ninc) is sensitive to the semantic and/or the response conflict. Consistent with our past findings (e.g., Augustinova et al. in Psychonomic Bulletin & Review 17:827-833, 2010), SLC speeded up reaction times for standard-incongruent items only, indicating that SLC reduced the response conflict that these (but not color-associated and neutral) items involve. Ninc amplitudes were more negative for standard-incongruent and color-associated than for color-neutral items. Importantly, this difference was not modulated by SLC. Hence, the behavioral and ERP results conjointly suggest that the Stroop-related Ninc is sensitive to semantic rather than to response and/or general conflict.
    No preview · Article · Aug 2014 · Psychonomic Bulletin & Review
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    • "In monolingual studies of conflict processing and executive control, the event-related potential (ERP) of primary interest is a more negative-going wave in incongruent trials as compared to congruent or control trials. In the Stroop task in particular, incongruency effects typically occur from approximately 300–550 ms post-stimulus over centro-parietal scalp [52]–[56]; this component is sometimes referred to as an N400 or N450. We refer to this conflict component in the Stroop task as the Ninc (a ‘negativity associated with incongruency’; see [57]) to avoid latency specifications and also to avoid confusion with the N400 component that is typically elicited by language and semantic processing (e.g. "
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    ABSTRACT: Bilinguals have been shown to exhibit a performance advantage on executive control tasks, outperforming their monolingual counterparts. Although a wealth of research has investigated this 'bilingual advantage' behaviourally, electrophysiological correlates are lacking. Using EEG with a Stroop task that manipulated the stimulus onset asynchrony (SOA) of word and colour presentation, the current study addressed two facets of the bilingual advantage. The possibility that bilinguals experience superior conflict processing relative to monolinguals (a 'conflict-specific advantage') was investigated by comparing behavioural interference effects as well as the amplitude of the Ninc, a conflict-related ERP component occurring from approximately 300-500 ms after the onset of conflict. In contrast, the hypothesis that bilinguals experience domain-general, conflict-independent enhancements in executive processing (a 'non-conflict-specific advantage') was evaluated by comparing the control condition (symbol strings) between groups. There was some significant, but inconsistent, evidence for a conflict-specific bilingual advantage. In contrast, strong evidence emerged for a non-conflict-specific advantage, with bilinguals demonstrating faster RTs and reduced ERP amplitudes on control trials compared to monolinguals. Importantly, when the control stimulus was presented before the colour, ERPs to control trials revealed group differences before the onset of conflict, suggesting differences in the ability to ignore or suppress distracting irrelevant information. This indicates that bilinguals experience superior executive processing even in the absence of conflict and semantic salience, and suggests that the advantage extends to more efficient proactive management of the environment.
    Full-text · Article · Jul 2014 · PLoS ONE
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    • "Despite conflict-related findings for the P1 component, the N450 component and the conflict sustained potential (henceforth Conflict-SP) [18], [29]–[35], consistently identified in the incongruent minus congruent differences wave, are the main ERP components associated with conflict processing. The N450 component is a negative-going ERP deflection appearing from approximately 350 to 500 ms post-stimulus at fronto-central sites. "
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    ABSTRACT: This study uses event-related brain potentials (ERPs) to investigate the electrophysiological correlates of numeric conflict monitoring in math-anxious individuals, by analyzing whether math anxiety is related to abnormal processing in early conflict detection (as shown by the N450 component) and/or in a later, response-related stage of processing (as shown by the conflict sustained potential; Conflict-SP). Conflict adaptation effects were also studied by analyzing the effect of the previous trial’s congruence in current interference. To this end, 17 low math-anxious (LMA) and 17 high math-anxious (HMA) individuals were presented with a numerical Stroop task. Groups were extreme in math anxiety but did not differ in trait or state anxiety or in simple math ability. The interference effect of the current trial (incongruent-congruent) and the interference effect preceded by congruence and by incongruity were analyzed both for behavioral measures and for ERPs. A greater interference effect was found for response times in the HMA group than in the LMA one. Regarding ERPs, the LMA group showed a greater N450 component for the interference effect preceded by congruence than when preceded by incongruity, while the HMA group showed greater Conflict-SP amplitude for the interference effect preceded by congruence than when preceded by incongruity. Our study showed that the electrophysiological correlates of numeric interference in HMA individuals comprise the absence of a conflict adaptation effect in the first stage of conflict processing (N450) and an abnormal subsequent up-regulation of cognitive control in order to overcome the conflict (Conflict-SP). More concretely, our study shows that math anxiety is related to a reactive and compensatory recruitment of control resources that is implemented only when previously exposed to a stimuli presenting conflicting information.
    Full-text · Article · May 2014 · PLoS ONE
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