The fractionation of executive functions : a study in a non clinical population

The conceptualisation of executive functioning has presented innumerable problems for the field of neuropsychology. Despite widespread use of the term 'executive function' in the literature, it is evident that there is a poor understanding of how to reliably describe, identify, or measure these skills. A review of available literature reveals that this can be attributed to a number of obstacles, which have clearly hindered progress. These include the heterogeneous nature of executive functions; a lack of clarifiction regarding the use of terminology; variability in existing theoretical, anatomical and functional definitions; and the questionable adequacy of executive function tests. Despite these overwhelming problems, researchers and clinicians are frequently faced with the challenge of providing accurate assessment of executive functions. It is apparent that one of the major obstacles preventing this is the provision of a comprehensive description of the component skills, which would provide the examiner knowledge of what cognitive functions need to be assesed. Given that significant developments are required before operationalisation in theoretical or anatomical terms can be achieved, it is proposed that a functional description of executive functions may present the best opportunity to define these skills. Unfortunately, given the inconsistency of reports in the literature, it is not possible to formulate such a definition based on a review of research findings. There is agreement, however, with respect to the tests that are commonly used to assess these skills. This may afford the opportunity to formulate a functional definition based upon the underlying cognitive skills that executive function tests measure. [...]