Effects of severe closed-head injury on three stages of information processing

The present study investigated the loci of the information-processing delay that characteristically follows severe closed-head injury (CHI). Sternberg's additive-factors logic was used to determine the effects of severe CHI on the central information-processing stages of stimulus encoding, memory comparison, and decision-making/response-selection. The task variables used to define the stages operationally were stimulus quality, memory set size, and stimulus-response compatibility. Twenty subjects who had sustained a severe CHI more than 18 months earlier and 20 matched control subjects completed a stimulus encoding by response selection task in Experiment 1, and a Sternberg high-speed memory scanning task in Experiment 2. The CHI group performed the stimulus encoding and decision-making/response-selection stages of processing significantly slower than did the control group. However, no significant group differences were found on the memory comparison stage, suggesting that memory comparison processes may be relatively intact in long-term patients with severe head trauma. The results are discussed in relation to a global and a late-specificity hypothesis of central processing deficits following severe CHI. The possibility that cognitive processes demanding less attention may be more resilient to injury is also considered.