fMRI Activations due to Attentional Selection can be Dependent upon Nature of Information to be Ignored.

Abstract:
This study determined whether common or distinct brain systems are activated as attentional selection increases in two Stroop-like tasks that differ in the unattended dimension. Both tasks required identification of an item's ink color, with a word being unattended in the color-word Stroop task and an object being unattended in the color-object Stroop task. For both tasks, we compared a neutral condition (e.g., the word "mass" in yellow ink; a yellow car) to an incongruent one (e.g., the word "blue" in yellow ink; a yellow frog). Both tasks activated similar regions of anterior cingulate cortex and prefrontal regions, contrasting with our prior Stroop fMRI study (Banich, et al., 1998) in which we found distinct regions of activation within these brain areas for two tasks that varied in the attended but not the unattended dimension. Like our prior study, however, both tasks activated different regions of parietal and occipito-temporal cortex. Only the word task activated precuneus regions while the object task activated the fusiform and lingual gyri. In tandem with our prior study, the results suggest that modulation of activity in frontal regions primarily depends upon the attended dimension, whereas activity in posterior regions reflects processing of both the attended and unattended dimensions.