Factors underlying neuropsychological test performance in chronic severe traumatic brain injury

The neuropsychological test performance of subjects with traumatic brain injury (TBI) of the closed head type was investigated using a test battery consisting of traditional clinical instruments with expanded language measures. TBI subjects were specifically selected to include only those with a pattern of predominantly diffuse cerebral injury to allow conclusions regarding language performance in the absence of focal aphasia-producing lesions. Factor analysis of the test scores resulted in the extraction of three interpretable factors associated with performance on this battery: perceptual, general language, and mental efficiency. The results were compared to those obtained in previous factor-analytic studies of brain-damaged subjects, revealing patterns for the language/verbal subtests that diverged from those observed formerly. Two explanations are considered for these findings, the first interpretation centering on the notion of select impairments to specific cognitive processes and the second relating to impairments in the capacity to allocate resources effectively.