Effects of closed-head injury on attentional processes: an information-processing stage analysis.

The present study, based on Sternberg's (1969) additive-factor method, examined attentional processes in terms of four information-processing stages (feature extraction, identification, response selection, and motor adjustment). Four task variables were used to operationally define the stages (signal quality, signal similarity, signal-response compatibility, and foreperiod uncertainty). In two studies, a visuo-spatial reaction-time task was undertaken by a group of university subjects (Experiment 1) and by three groups of closed-head-injured patients (severe short-term, severe long-term, and mild short-term) and their corresponding matched controls (Experiment 2). The results indicated that both patients and normals exhibited a similar mode of linear information processing. In addition, it was found that the severe short-term group was impaired on the response-selection stage and response selection stage; the severe long-term group was impaired only on the response-selection; and no evidence of impairment was found for the mild short-term patients. The implications of these findings with reference to the study of attentional processes in closed-head injured patients and to neuropsychological assessment and rehabilitation are discussed.