Traumatic brain injury (TBI) is frequently associated with both cognitive and behavioural executive dysfunction. Assessment of executive dysfunction has traditionally been measured using tests that were not based on theory and this has been postulated as one reason why there are poor predictive relationships between performance on traditional executive tasks and functional outcome following TBI. Baddeley�s (1996) working memory model may offer a theoretical basis with which to design new executive measures and possibly improve prediction of outcome. Baddeley�s theory has made recent advances in identifying core central executive (CE) processes that are likely to be relevant to TBI. The research presented in the thesis used Baddeley�s proposed coordinative sub function of the CE (and it related dual tasking measure) to assess: (a) whether this theoretically based dual tasking test would be sensitive to TBI injury status and show a significant relationship with functional outcome, (b) whether the theoretically based test would be more sensitive to the above relationships than executive measures that have been traditionally available, and (c) whether more ecologically relevant dual tasks could be developed that reflect the coordinative construct and improve predictive relationships between task performance and real life functional ability. This study found that Baddeley�s Dual Task Test (DTT) measure was sensitive to TBI injury and was related to functional outcome following injury. A questionnaire assessing everyday dual tasking ability was developed as was an in vivo conversation and motor based dual task. The dual tasking questionnaire reflected Baddeley�s coordinative construct, however, applications to an in vivo conversation and motor based dual task were less successful. These ecologically relevant tasks showed a relationship between language dysfluencies and dual tasking and identified avoidance of dual tasking in everyday settings as an important predictor of functional outcome following injury. Overall the DTT and the dual tasking questionnaire showed greater injury sensitivity and stronger relationships with outcome than three executive measures traditionally used in clinical practice. Regression analysis confirmed that the dual based tasks were helpful in predicting a variety of outcomes following TBI, and implications for rehabilitation planning are discussed. Further increases in the predictive power of the dual tasking construct are likely to be achieved when mechanisms of action involved in both laboratory-based and real-life dual tasking are identified. Findings from the current study suggest a range of mechanisms could be involved in dual tasks and these are discussed.

Traumatic brain injury (TBI) is frequently associated with both cognitive and behavioural executive dysfunction. Assessment of executive dysfunction has traditionally been measured using tests that were not based on theory and this has been postulated as one reason why there are poor predictive relationships between performance on traditional executive tasks and functional outcome following TBI. Baddeley�s (1996) working memory model may offer a theoretical basis with which to design new executive measures and possibly improve prediction of outcome. Baddeley�s theory has made recent advances in identifying core central executive (CE) processes that are likely to be relevant to TBI. The research presented in the thesis used Baddeley�s proposed coordinative sub function of the CE (and it related dual tasking measure) to assess: (a) whether this theoretically based dual tasking test would be sensitive to TBI injury status and show a significant relationship with functional outcome, (b) whether the theoretically based test would be more sensitive to the above relationships than executive measures that have been traditionally available, and (c) whether more ecologically relevant dual tasks could be developed that reflect the coordinative construct and improve predictive relationships between task performance and real life functional ability. This study found that Baddeley�s Dual Task Test (DTT) measure was sensitive to TBI injury and was related to functional outcome following injury. A questionnaire assessing everyday dual tasking ability was developed as was an in vivo conversation and motor based dual task. The dual tasking questionnaire reflected Baddeley�s coordinative construct, however, applications to an in vivo conversation and motor based dual task were less successful. These ecologically relevant tasks showed a relationship between language dysfluencies and dual tasking and identified avoidance of dual tasking in everyday settings as an important predictor of functional outcome following injury. Overall the DTT and the dual tasking questionnaire showed greater injury sensitivity and stronger relationships with outcome than three executive measures traditionally used in clinical practice. Regression analysis confirmed that the dual based tasks were helpful in predicting a variety of outcomes following TBI, and implications for rehabilitation planning are discussed. Further increases in the predictive power of the dual tasking construct are likely to be achieved when mechanisms of action involved in both laboratory-based and real-life dual tasking are identified. Findings from the current study suggest a range of mechanisms could be involved in dual tasks and these are discussed.