Interrupting the "stream of consciousness": an fMRI investigation.
NeuroImage February 15, 2006 Kristen A McKiernan, Benjamin R D'Angelo, Jacqueline N Kaufman et al.
During demanding cognitive tasks, certain brain regions show reduced blood flow compared to resting states, a phenomenon called task-induced deactivation (TID). This study investigated whether TID reflects a suspension of internally focused thought. Using an auditory detection task with seven difficulty levels, participants reported task-unrelated thoughts (TUTs) at intervals. Fewer TUTs occurred during harder conditions, and as TID magnitude increased across conditions, TUT frequency declined (r = 0.90). Four left hemisphere regions—posterior parieto-occipital cortex, anterior cingulate gyrus, fusiform gyrus, and middle frontal gyrus—showed strong correlations between TUTs and TID. These regions are linked to semantic and self-referential processing, supporting the idea that TID arises from suspending internal cognitive activity.