THE EFFECTS OF FOCAL AND DIFFUSE BRAIN-DAMAGE ON STRATEGY APPLICATION- EVIDENCE FROM FOCAL LESIONS, TRAUMATIC BRAIN INJURY AND NORMAL AGING

A new test of strategy application was designed to be relatively free of the constraints that limit the standard neuropsychological assessme nt of supervisory abilities. The validity of the test was assessed in 3 samples of participants with varying degrees of supervisory deficits and frontal systems dysfunction: focal frontal lesions, traumatic bra in injury (TBI), and normal aging. Inefficient strategy application va ried systematically across the 3 groups and was not due to extraneous factors such as forgetting the test instructions. Previous case studie s have emphasized strategy application deficits in the face of normal neuropsychological test performance. In this study, it was shown that strategically impaired participants from a consecutive series can incl ude those both with and without deficient neuropsychological test perf ormance. When neuropsychological impairment was present, it was greate st on executive functioning tasks. Among participants with nonstrategi c performance, there was evidence for a dissociation of knowledge from action. This finding was not specific to focal frontal lesions. A num ber of supervisory processes contributing to strategy application were identified. Exploratory analyses indicated differential effects of le sion location on these processes, especially inferior medial frontal a nd right hemisphere lesions. Overall, the results supported the use of unstructured tasks in the assessment of supervisory abilities.