Rapid Modulation of Sensory Processing Induced by Stimulus Conflict

Duke University, Durham, NC 27708, USA.
Journal of Cognitive Neuroscience (Impact Factor: 4.09). 09/2011; 23(9):2620-8. DOI: 10.1162/jocn.2010.21575
Source: DBLP


Humans are constantly confronted with environmental stimuli that conflict with task goals and can interfere with successful behavior. Prevailing theories propose the existence of cognitive control mechanisms that can suppress the processing of conflicting input and enhance that of the relevant input. However, the temporal cascade of brain processes invoked in response to conflicting stimuli remains poorly understood. By examining evoked electrical brain responses in a novel, hemifield-specific, visual-flanker task, we demonstrate that task-irrelevant conflicting stimulus input is quickly detected in higher level executive regions while simultaneously inducing rapid, recurrent modulation of sensory processing in the visual cortex. Importantly, however, both of these effects are larger for individuals with greater incongruency-related RT slowing. The combination of neural activation patterns and behavioral interference effects suggest that this initial sensory modulation induced by conflicting stimulus inputs reflects performance-degrading attentional distraction because of their incompatibility rather than any rapid task-enhancing cognitive control mechanisms. The present findings thus provide neural evidence for a model in which attentional distraction is the key initial trigger for the temporal cascade of processes by which the human brain responds to conflicting stimulus input in the environment.

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Available from: Lawrence Gregory Appelbaum, May 08, 2014
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    • "They found that load interacted with distractor congruency, such that BOLD signals in area V1 were greater to incongruent than congruent distractors under conditions of high (versus low) working memory load. Appelbaum et al. (2011) used EEG recording to examine the event-related potentials (ERPs) evoked by lateralized letter flankers. They found a lateralized change in voltage over the occipital cortex in the presence of incongruent flankers, which co-occurred with fronto-parietal voltage changes typically observed in studies of response conflict. "
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    ABSTRACT: The brain is frequently confronted with sensory information that elicits conflicting response choices. While much research has addressed the top down control mechanisms associated with detection and resolution of response competition, the effects of response competition on sensory processing in primary visual cortex remain unclear. To address this question we modified a typical 'flanker task' (Eriksen & Eriksen, 1974) so that the effects of response competition on human early retinotopic visual cortex could be assessed. Healthy human participants were scanned using fMRI while making a speeded choice response that classified a target object image into one of two categories (e.g. fruits, animals). An irrelevant distractor image that was either congruent (same image as target), incongruent (image from opposite category as target), or neutral (image from task-irrelevant category, e.g. household items) was also present on each trial, but in a different quadrant of the visual field relative to the target. Retinotopic V1 areas responding to the target stimuli showed increased response to targets in the presence of response-incongruent (compared to response-neutral) distractors. A negative correlation with behavioral response competition effects indicated that an increased primary visual cortical response to targets in the incongruent (vs. neutral) trials is associated with a reduced response competition effect on behavior. These results suggest a novel conflict resolution mechanism in primary visual cortex.
    NeuroImage 05/2013; 81(100). DOI:10.1016/j.neuroimage.2013.04.094 · 6.36 Impact Factor
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    • "The first of these mechanisms, target amplification, facilitates and strengthens the neural activity associated with relevant stimuli [7]–[9]. The second, distractor inhibition, reduces the strength of the neural activity associated with irrelevant stimuli [5], [6], [10]–[14]. These mechanisms both function to aid selective attention, yet they are distinct and work independently of each other [15]–[19]. "
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    ABSTRACT: Along with target amplification, distractor inhibition is regarded as a major contributor to selective attention. Some theories suggest that the strength of inhibitory processing is proportional to the salience of the distractor (i.e., inhibition reacts to the distractor intensity). Other theories suggest that the strength of inhibitory processing does not depend on the salience of the distractor (i.e., inhibition does not react to the distractor intensity). The present study aimed to elucidate the relationship between the intensity of a distractor and its subsequent inhibition during focused attention. A flanker task with a variable distractor-target stimulus-onset asynchrony (SOA) was used to measure both distractor interference and distractor inhibition. We manipulated the intensity of the distractor in two separate ways, by varying its distance from the target (Experiment 1) and by varying its brightness (Experiment 2). The results indicate that more intense distractors were associated with both increased interference and stronger distractor inhibition. The latter outcome provides novel support for the reactive inhibition hypothesis, which posits that inhibition reacts to the strength of distractor input, such that more salient distractors elicit stronger inhibition.
    PLoS ONE 04/2013; 8(4):e62809. DOI:10.1371/journal.pone.0062809 · 3.23 Impact Factor
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    • "While the conflict-monitoring model views CSEs explicitly as an expression of across-trial processing adjustments (Botvinick et al., 2001), it should be noted that the current results are also compatible with the possibility that conflict adaptation occurs within trial n-1 and it is the steadily decaying aftereffects of such within-trial control processes that produce the CSE on trial n. Some recent work has produced support for the basic existence of rapid within-trial processing adjustments (Taylor et al., 2007; Appelbaum et al., in press), and has suggested that these may be mediated by principally distinct mechanisms than those that underpin across-trial adjustments (Boy et al., 2010). However, whether CSEs are an expression of the former or the latter currently remains an open question. "
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    ABSTRACT: Performance on traditional selective attention tasks, like the Stroop and flanker protocols, is subject to modulation by trial history, whereby the magnitude of congruency (or conflict) effects is often found to decrease following an incongruent trial compared to a congruent one. These "congruency sequence effects" (CSEs) typically appear to reflect a mesh of memory- and attention-based processes. The current study aimed to shed new light on the nature of the attention-based contribution to CSEs, by characterizing the shape of the CSE time-course while controlling for mnemonic influences. Existing attention-based accounts of CSEs are either ambiguous in their predictions of CSE time-courses, or predict CSEs to persist or grow over the post-stimulus/response interval in anticipation of an upcoming stimulus. We gauged CSE time-courses by systematically varying inter-stimulus (Experiment 1) and response-to-stimulus (Experiment 2) intervals across a wide temporal range, in a face-word Stroop task. In spite of an exponential increase in the likelihood of stimulus appearance with increasing interval duration (i.e., an exponential hazard function), results from both experiments showed CSEs to be most pronounced at the shortest intervals, to quickly decay in magnitude with increasing interval length, and to be absent at longer intervals. These data refute the idea that attentional contributions to CSEs remain static over post-stimulus/response intervals and are incompatible with the notion that CSEs reflect expectation-guided preparatory biasing in anticipation of a forthcoming stimulus. The data are compatible, however, with the notion that attentional contributions to CSEs reflect a short-lived, phasic enhancement of attentional set in reaction to processing conflict.
    Frontiers in Psychology 09/2010; 1:154. DOI:10.3389/fpsyg.2010.00154 · 2.80 Impact Factor
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