Neural correlates of dual task interference can be dissociated from those of divided attention: an fMRI study

When people perform two tasks simultaneously, the tasks are often executed slower and with more errors than when they are carried out as single tasks. This is called dual task interference. With functional magnetic resonance imaging (fMRI), we show that concurrently performed visual and somatosensor y reaction time (RT) tasks engage almost identical volumes of cortical and subcortical motor structures. Moreover, dual RT tasks engaged additional co rtical regions that are not activated by the component RT tasks had they be en performed as single tasks. When the inter-stimulus interval was < 300 ms , the first task interfered with the second, and a field in the right infer ior frontal gyrus (RIFG) appeared with activity correlated with the increas ed RT to the second stimulus. This activation was spatially distinct from t he cortical activity of the main effect of dual task performance. Thus, the performance of single RT tasks, dual RT tasks and dual HT tasks that inter fere differ psychophysically and in the brain structures subserving these t asks. A short occupancy of the common motor structures can explain the inte rference effect. The increased activity of the RIFG correlated with the int erference effect is very likely to he a specific outcome of situations wher e two concurrent tasks interfere with each other. The brain appears to recr uit the RIFG for a subsequent (delayed) response when there is interference between dual tasks.