Impaired recognition memory after head injury.

A continuous recognition memory task employing 120 line drawings of familiar stimuli was administered to patients recovering from closed head injury of varying severity and control patients. Mildly injured patients obtained significantly more correct responses, and higher memory sensitivity (d') values than moderately and severely injured patients who performed similarly. The measure of response criterion, c, was significantly lower in patients with injury of moderate severity when compared to mildly injured cases and control patients. Controls and mildly injured patients did not differ in their performance. In general, the total correct responses most impressively differentiated head injured patients with measurable coma duration as more than two-thirds had scores below the control group. Group differences in hits, false alarms and misses were examined also. Age and education, skull fracture, and hematoma were generally unrelated to any of the measures, whereas coma duration was significantly related to most measures of mnemonic efficiency.