Working memory and executive control.

A major problem in analysing the executive processes that seem to depend upon the prefrontal cortex stems from the absence of a well developed cognitive model of such processes. It is suggested that the central executive component of an earlier model of working memory might provide a suitable framework for such an analysis. The approach is illustrated using one proposed component of executive control, namely the capacity to combine two concurrent tasks. The application of the approach to patients suffering from Alzheimer's disease, and patients with acquired brain damage is discussed. Finally, a study is described in which the dual task performance of patients with known frontal lesions is shown to be associated with observed behavioural problems. The paper concludes with the discussion of the prospects for extending the approach to include a range of other executive processes, and to the way in which such an analysis may subsequently lead to a more integrated model of the central executive, and a better understanding of its relationship to the prefrontal cortex.