Word and position interference in stroop tasks: a behavioral and fMRI study.

One of the main features of the attentional system is the capability to select between relevant and irrelevant information. However, irrelevant information interferes with the processing of the relevant one. Using high-field magnetic resonance imaging, we examined the interference effect of a verbal (color-word) and a spatial (arrow-position) Stroop task on the activation of cortical areas known to be dedicated to the attentional control. Behaviorally, we found costs from the irrelevant information in both tasks; in the brain, we found a common neural network of activation that mainly involved the dorsolateral prefrontal cortex and the anterior cingulate cortex. However, the neural circuits involved in the two tasks overlapped only partially, since processing of words in the color-word Stroop task showed a wider and more right-lateralized activation, while spatial processing in the arrow-position Stroop task resulted in a more restricted and left-lateralized activation.