Elsevier

Neuropsychologia

Volume 46, Issue 12, October 2008, Pages 2872-2879
Neuropsychologia

Processing conflicting information: Facilitation, interference, and functional connectivity

https://doi.org/10.1016/j.neuropsychologia.2008.05.025Get rights and content

Abstract

When a conflict task involves congruent, neutral, and incongruent conditions, it is possible to examine facilitation (neutral vs. congruent) and interference (incongruent vs. neutral) components. Very few studies investigated the brain areas that are specifically involved in facilitation or interference. We used functional magnetic resonance imaging while participants performed a magnitude conflict task (the size congruity paradigm). We observed four findings: (1) while most of the brain areas that were activated by conflict tasks showed interference effects, the intraparietal sulcus was the only region activated for both interference and facilitation components. (2) Two groups of participants could be distinguished based on the pattern of anterior cingulate cortex (ACC) activity, one with classical facilitation (congruent < neutral), one with reverse facilitation. (3) Functional connectivity analysis of the areas that were modulated by the conflict task revealed an anterior cingulate – lateral prefrontal cortex network and a dorsal parietal – premotor cortex network. We suggest that the former plays a role in cognitive control and conflict detection, whereas the latter participates in top–down selection of task-relevant stimuli and response mapping. (4) These networks were modulated by the two groups that we distinguished based on the ACC activation.

Section snippets

The size congruity paradigm

In the current study we used another conflict paradigm, the size congruity paradigm. In this paradigm, participants had to compare either the numerical value or the physical size of two digits. They indicated their choices by pressing one of two keys corresponding to the side of the display with the selected digit. The two digits differed in both numerical value and physical size, which amounted to a Stroop-like situation (Cohen Kadosh, 2008; Cohen Kadosh, Cohen Kadosh, Linden et al., 2007;

Until what stage does conflict continue?

In a recent study of the SCE (Cohen Kadosh et al., 2007a), we examined whether the conflict between the numerical and the physical comparison occurs at a response-related stage or earlier (e.g., a conceptual stage) by using event-related potential (ERP) and functional magnetic resonance imaging (fMRI). In the fMRI we examined the blood oxygenation level-dependent (BOLD) signal in the motor cortex, using a measure that is equivalent to the lateralized BOLD response (LBR) (Dehaene et al., 1998).

Materials and methods

We analysed fMRI data from a previous study (Cohen Kadosh et al., 2007a) where the general methods were described in full.

Behavioral data

For every participant in each condition the mean RT was calculated for correct trials only. The two-way interaction between task and congruency was not significant (F < 1, p > .2). The main effect for congruency was significant [F(2, 26) = 118.40, p < 0.001, Fig. 1]. Planned comparisons revealed that participants were significantly slower in incongruent than neutral conditions (interference) [F(1, 13) = 76.63, p < .001]. Conversely, they were significantly faster in congruent than neutral conditions

Discussion

We employed the size congruity paradigm to reveal brain areas that are modulated by facilitation and interference in a conflict task, and the functional connectivity of the conflict monitoring and resolution areas.

Conflict of interest

None.

Acknowledgements

The authors wish to thank Vincent van de Ven for help with the functional connectivity analysis, Desiree Meloul and the anonymous referees for valuable comments.

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