Article

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

ABSTRACT

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.
    Full-text · Article · May 2013 · NeuroImage
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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.
    Full-text · Article · Apr 2013 · PLoS ONE
    • "For example, the fact of either repeating a task across two successive trials or switching from one task to another can dramatically influence performance, such that reaction times and error rates both increase after switching to perform a new task—i.e., the switch cost effect [reviewed in Wylie and Allport, 2000]. The importance of top-down control for stimulus processing has been broadly studied in cognitive control research using interference paradigms, where congruence between different dimensions of two unisensory stimuli is manipulated [e.g., the flanker task; Appelbaum et al., 2011; Corballis and Gratton, 2003]. Real-world environments are typically multisensory in nature and therefore congruence (or lack thereof) permeates it. "
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    ABSTRACT: In a previous behavioural study, we reported that a particular context of stimulus congruency influenced audiovisual interactions. In particular, audiovisual interaction, measured in terms of congruency effect, was reduced when a high proportion of incongruent trials was presented. We argued that this modulation was due to changes in participants' control set as a function of the context of congruency, with greater control applied when most of the trials were incongruent. Since behavioural data do not allow to specify the level at which control was affecting audiovisual interaction, we conducted an event-related potentials (ERPs) study to further investigate each context of audiovisual congruency. Participants performed an audiovisual congruency task, where the stimulus onset could be present on two different contexts mixed at random: a high proportion congruent context and a low proportion congruent context. The context manipulation was found to modulate brain ERPs related to perceptual and response selection processes, ie, the N2 and P3 components. The N2 amplitude was larger for the less common trials on both high and low congruent proportion contexts, while the P3 amplitude and latency were differentially modulated by incongruent trials on the two contexts.
    No preview · Article · Oct 2011 · i-Perception
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