Frontiers in Human Neuroscience (Sep 2013)
Behavioural and neural interaction between spatial inhibition of return and the Simon effect
Abstract
It has been well documented that the anatomically independent attention networks in the human brain interact functionally to achieve goal-directed behaviours. By combining spatial inhibition of return (IOR) which implicates the orienting network with some executive function tasks (e.g., the Stroop and the flanker effects) which implicate the executive network, researchers consistently found that the interference effects are significantly reduced at cued compared to uncued locations, indicating the functional interaction between the two attention networks. However, a unique, but consistent, effect is observed when spatial IOR is combined with the Simon effect: the Simon effect is significantly higher at the cued than uncued locations. To investigate the neural substrates underlying this phenomenon, we orthogonally combined the spatial IOR with the Simon effect in the present event-related fMRI study. Our behavioural data replicated previous results by showing larger Simon effect at the cued location. At the neural level, we found shared spatial representation system between spatial IOR and the Simon effect in bilateral posterior parietal cortex; spatial IOR specifically activated bilateral superior parietal cortex while the Simon effect specifically activated bilateral middle frontal cortex. Moreover, left precentral gyrus was involved in the neural interaction between spatial IOR and the Simon effect by showing significantly higher neural activity in the ‘Cued_Congruent’ condition. Taken together, our results suggest that due to the shared spatial representation system in the posterior parietal cortex, responses were significantly facilitated when spatial IOR and the Simon effect relied on the same spatial representations, i.e., in the ‘Cued_Congruent’ condition. Correspondingly, the sensorimotor system was significantly involved in the ‘Cued_Congruent’ condition to fasten the responses, which indirectly resulted in the enhanced Simon effect at the cued location.
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