Examining executive function in individuals with brain injury: A review

Background: Patients with aphasia resulting from a stroke may exhibit cognitive impairments in addition to their language disturbance. The ability to detect and quantify executive function impairment, in particular, may be critical to treating these patients. Furthermore, the effects of executive dysfunction on daily activities may interact with or amplify limitations due to their language disorder. Multiple measures exist in the clinical and research neuropsychological literatures for assessing executive function, however these vary in reliability, validity, and language demands. Aims: This review explores the definition of executive function, describes tests of executive function, and makes recommendations regarding their use in populations with language impairment. Initially a literature search was undertaken for reviews and empirical studies addressing the definition and measurement of executive function, as well as studies of cognitive function in patients with frontal lobe damage. Included in this review are tasks on which patients with frontal lesions showed impairments, activations were seen in neuroimaging studies, or which were developed for the purpose of tapping a cognitive process hypothesized to be an executive function. Main contribution: Studies of cognitive ability in those with aphasia are reviewed. Purported executive function tests are organized into a proposed substructure for grouping executive processes, and are evaluated for their usefulness in assessing those with aphasia. Tests that have been used hint at impairments in some individuals with aphasia, suggesting a need to look at correlation with severity of auditory comprehension and constructional praxis. Conclusions: Although few executive function tests are currently appropriate for use in a language-disordered population without modifications, many have potential. In order to advance our understanding of the construct of executive function, it is important to develop a clearer definition of the processes involved. In the meantime, the tests reviewed here may be helpful in assessing whether cognitive impairment exists in addition to the language dysfunction in those with aphasia.