The Role of Stimulus Salience and Attentional Capture Across the Neural Hierarchy in a Stop-Signal Task

Center for Cognitive Neuroscience, Duke University, Durham, North Carolina, United States of America.
PLoS ONE (Impact Factor: 3.23). 10/2011; 6(10):e26386. DOI: 10.1371/journal.pone.0026386
Source: PubMed


Inhibitory motor control is a core function of cognitive control. Evidence from diverse experimental approaches has linked this function to a mostly right-lateralized network of cortical and subcortical areas, wherein a signal from the frontal cortex to the basal ganglia is believed to trigger motor-response cancellation. Recently, however, it has been recognized that in the context of typical motor-control paradigms those processes related to actual response inhibition and those related to the attentional processing of the relevant stimuli are highly interrelated and thus difficult to distinguish. Here, we used fMRI and a modified Stop-signal task to specifically examine the role of perceptual and attentional processes triggered by the different stimuli in such tasks, thus seeking to further distinguish other cognitive processes that may precede or otherwise accompany the implementation of response inhibition. In order to establish which brain areas respond to sensory stimulation differences by rare Stop-stimuli, as well as to the associated attentional capture that these may trigger irrespective of their task-relevance, we compared brain activity evoked by Stop-trials to that evoked by Go-trials in task blocks where Stop-stimuli were to be ignored. In addition, region-of-interest analyses comparing the responses to these task-irrelevant Stop-trials, with those to typical relevant Stop-trials, identified separable activity profiles as a function of the task-relevance of the Stop-signal. While occipital areas were mostly blind to the task-relevance of Stop-stimuli, activity in temporo-parietal areas dissociated between task-irrelevant and task-relevant ones. Activity profiles in frontal areas, in turn, were activated mainly by task-relevant Stop-trials, presumably reflecting a combination of triggered top-down attentional influences and inhibitory motor-control processes.

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Available from: Lawrence Gregory Appelbaum, May 08, 2014
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    • "Although common activation during behavioral inhibition in go/no-go- and stop-signal tasks has been shown in clusters in the right VLPFC, IFJ, and pre-SMA (Rubia et al., 2001; Swick et al., 2011; Sebastian et al., 2013b), increased activation during inhibition in a stop-signal task as compared to the go/no-go task has been reported in the right VLPFC, left insula, and the pre-SMA (Swick et al., 2011; Sebastian et al., 2013b). Activation in the IFJ during behavioral inhibition has rather been linked to attentional processes than to inhibitory functioning (Chikazoe et al., 2008; Verbruggen et al., 2010; Boehler et al., 2011). "
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    • "Theories on motor inhibition and response-switching via stimulus-response mapping have been developed separately and only few studies[14]–[16]have investigated how changing stimulus-response (S-R) mapping influences the inhibition process. Others have investigated the role of stop-signal relevance [17], how preparation influences the inhibition processes [18], [19], as well as probability effects in the stop-signal paradigm [20], [21].Probability, or frequency, effects in the stop-signal task have typically been studied with electroencephalography(EEG) methods and the functional magnetic resonance imaging (fMRI) literature for this particular topic is relatively sparse. Although both stop signal relevance and frequency seem to influence the inhibition processes, it remains to be determined whether these two key features interact and whether or not they exert an influence on stopping processes either at the behavioral or neurophysiological levels. "
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    ABSTRACT: Humans are rarely faced with one simple task, but are typically confronted with complex stimulus constellations and varying stimulus-relevance in a given situation. Through modifying the prototypical stop-signal task and by combined recording and analysis of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), we studied the effects of stimulus relevance for the generation of a response or its inhibition. Stimulus response mappings were modified by contextual cues, indicating which of two different stimuli following a go stimulus was relevant for stopping. Overall, response inhibition, that is comparing successful stopping to a stop-signal against go-signal related processes, was associated with increased activity in right inferior and left midfrontal regions, as well as increased EEG delta and theta power; however, stimulus-response conditions in which the most infrequent stop-signal was relevant for inhibition, were associated with decreased activity in regions typically involved in response inhibition, as well as decreased activity in the delta and theta bands as compared to conditions wherein the relevant stop-signal frequency was higher. Behaviorally, this (aforementioned) condition, which demanded inhibition only from the most infrequent stimulus, was also associated with reduced reaction times and lower error rates. This pattern of results does not align with typical stimulus frequency-driven findings and suggests interplay between task relevance and stimulus frequency of the stop-signal. Moreover, with a multimodal EEG-fMRI analysis, we demonstrated significant parameterization for response inhibition with delta, theta and beta time-frequency values, which may be interpreted as reflecting conflict monitoring, evaluative and/or motor processes as suggested by previous work (Huster et al., 2013; Aron, 2011). Further multimodal results suggest a possible neurophysiological and behavioral benefit under conditions whereby the most infrequent stimulus demanded inhibition, indicating that the frequency of the stop-signal interacts with the current stimulus-response contingency. These results demonstrate that response inhibition is prone to influence from other cognitive functions, making it difficult to dissociate real inhibitory capabilities from the influence of moderating mechanisms.
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