Resolving dual-task interference: an fMRI study.

The human cognitive system is severely limited in the amount of information it can process simultaneously. When two tasks are presented within a short stimulus-onset-asynchrony (SOA), reaction time of each task, especially task 2, is dramatically delayed. Previous studies have shown that such delay is accompanied by increased activation in the right inferior frontal gyrus (GFi). In this study, we address the role of right GFi in resolving dual-task interference at two different stages: allocation of perceptual attention and response selection. We scan 12 subjects using functional MRI while they conduct two tasks-shape discrimination in task 1 and color discrimination in task 2-and vary the SOA between tasks as 100 or 1500 ms. The targets are located at the center or at the periphery. When both are at the center, they compete primarily for response selection. When both are at the periphery, they additionally compete for the allocation of perceptual attention. Results show that the right GFi and frontal operculum regions are significantly more active in the short SOA than the long SOA condition, but only when subjects attend to the periphery in both tasks. We conclude that the right lateral frontal regions are important for resolving dual-task interference at the perceptual attention stage.