Acquisition versus retrieval deficits in traumatic brain injury: Implications for memory rehabilitation

Objective: To examine whether impaired memory in persons with traumatic bra in injury (TBI) is caused by impaired initial acquisition or compromised re trieval from long-term storage. Design: Prospective matched controlled trial. Setting: Postacute rehabilitation institute. Participants: Patients with moderate to severe TBI (n = 28) and 21 matched, healthy controls (HCs). Main Outcome Measures: Patients with TBI and HC subjects were equated on in itial acquisition on a verbal list-learning task. Recall and recognition pe rformance was then evaluated at 30- and 90-minutes after learning. Results: All HC subjects and 20 subjects with TBI (TBI-MET) were able to me et the learning criterion, but the TBI-MET group took significantly more tr ials than HC subjects to do so. However, after equating groups on acquisiti on, the TBI-MET group did not differ from controls on recall and recognitio n at both the 30- and 90-minute delays. Eight TBI subjects showed severe le arning deficits (TBI-NOT MET) because they never learned the task, and show ed significantly impaired recall and recognition performance. The 2 TBI gro ups did not differ on measures of severity of injury, but the TBI-NOT MET g roup performed significantly below the TBI-MET group on executive functioni ng. Rate of forgetting did not differ across the 3 groups. Conclusions: Results suggest that memory impairment after TBI is caused pri marily by deficiencies in initial acquisition of verbal information rather than in compromised retrieval. The findings have significant implications f or the rehabilitation and treatment of individuals with TBI.