Functional neuroanatomy of executive processes involved in dual-task performance

The subjective experience of allocating one's attentional resources among c ompeting tasks is nearly universal, and most current models of cognition in clude a mechanism that performs this allocation; examples include the centr al executive system and the supervisory attentional system. Yet, the exact form that an executive system might take and even its necessity for cogniti on are controversial. Dual-task paradigms have commonly been used to invest igate executive function. The few neuroimaging studies of these paradigms h ave yielded contradictory findings. Using functional MRI, we imaged brain f unction during two dual-task paradigms, each with a common auditory compone nt task (NOUN task) but varying with respect to a Visual component task (SP ACE or FACE tasks). In each of the two dual-task paradigms, the results sho wed that the activated areas varied with the component tasks, that all of t he areas activated during dual task performance were also activated during the component tasks, and that surplus activation within activated areas dur ing DUAL conditions was parsimoniously accounted for by the addition of the second task. These findings suggest that executive processes may be mediat ed by interactions between anatomically and functionally distinct systems e ngaged in performance of component tasks, as opposed to an area or areas de dicated to a generic executive system.