The effects of mild and severe traumatic brain injury on speed of information processing as measured by the computerized tests of information processing (CTIP).

In spite of the fact that reaction time (RT) measures are sensitive to the effects of traumatic brain injury (TBI), few RT procedures have been developed for use in standard clinical evaluations. The computerized test of information processing (CTIP) [Tombaugh, T. N., & Rees, L. (2000). Manual for the computerized tests of information processing (CTIP). Ottawa, Ont.: Carleton University] was designed to measure the degree to which TBI decreases the speed at which information is processed. The CTIP consists of three computerized programs that progressively increase the amount of information that is processed. Results of the current study demonstrated that RT increased as the difficulty of the CTIP tests increased (known as the complexity effect), and as severity of injury increased (from mild to severe TBI). The current study also demonstrated the importance of selecting a non-biased measure of variability. Overall, findings suggest that the CTIP is an easy to administer and sensitive measure of information processing speed.

The effects of mild and severe traumatic brain injury on the auditory and visual versions of the Adjusting-Paced Serial Addition Test (Adjusting-PSAT).

Auditory and visual versions of the Adjusting-PSAT [Tombaugh, T. N. (1999). Administrative manual for the adjusting-paced serial addition test (Adjusting-PSAT). Ottawa, Ontario: Carleton University] were used to examine the effects of mild and severe traumatic brain injury (TBI) on information processing. The Adjusting-PSAT, a computerized modification of the original PASAT [Gronwall, D., & Sampson, H. (1974). The psychological effects of concussion. Auckland, New Zealand: Auckland University Press], systematically varied the inter-stimulus interval (ISI) by making the duration of the ISI contingent on the correctness of the response. This procedure permitted calculation of a temporal threshold measure that represented the fastest speed of digit presentation at which a person was able to process the information and provide the correct answer. Threshold values progressively declined as a function of the severity of TBI with visual thresholds significantly lower than auditory thresholds. The major importance of the current study is that the threshold measure offers a potentially more precise way of evaluating how TBI affects cognitive functioning than is achieved using the traditional PASAT and the number of correct responses. The Adjusting-PSAT offers the additional clinical advantages of eliminating the need to make a priori decisions about what ISI should be used in different clinical applications, and avoiding spuriously high levels of performance that occur when an "alternate answer" or chunking strategy is used. Unfortunately, the Adjusting-PSAT did not reduce the high level of frustration previously associated with the traditional PASAT.