WORKING-MEMORY IMPAIRMENTS IN TRAUMATIC BRAIN INJURY - EVIDENCE FROM A DUAL-TASK PARADIGM

Although many individuals with traumatic brain injury (TBI) perform we ll on standard neuropsychological tests, they often exhibit marked fun ctional difficulties. The functions which are impaired seem to be anal ogous to the role of the central executive system (CES) in Baddeley's [Working Memory, 1986, Oxford University Press, New York] widely accep ted model of working memory. The purpose of this study was to investig ate CES function in individuals with TBI with a dual-task paradigm. We studied 25 non-demented persons who were at various stages in their r ecovery from severe TBI and compared their performance on a dual-task paradigm to a group of age-matched controls. Our dual-task paradigm me asured performance on a simple visual reaction time task both alone (b aseline) and during concurrent tasks of articulation or digit span. Su bjects were also assessed with other neuropsychological tests of execu tive function. TBI patients had slower reaction times on the primary t ask when performed alone (P<0.05) and greater decrements in performanc e during dual-task conditions (P<0.01). They also exhibited significan tly greater deficits than control subjects on other measures of execut ive function. Although correlations between dual-task performance and other executive measures were quite low, principle components analysis suggested that a common factor does exist between these measures. The se findings support the conclusion that TBI patients have a working me mory impairment that is due to dysfunction of the CES and which may be related to executive function deficits as measured by standard neurop sychological testing. (C) 1997 Elsevier Science Ltd.