Verbal Learning and Memory in Adults with Mild, Moderate and Severe Closed Head Injury

One of the most prevalent of cognitive dysfunctions associated with closed head injury is impaired_memory function. The current study examined qualitative and quantitative aspects of learning and memory to define the effects of mild head injury in comparison to moderate and severe head injury and a sample of normal controls. Forty five survivors of severe (n=15), moderate (n=15) and mild (n=15) closed head injury were compared with age and education matched controls (n=15) on the California Verbal Learning Test (CVLT) and the Wechsler Memory Scale (WMS). On CVLT learning trials, head injured groups recalled less than controls, with the severely head injured showing poorest recall. Proportion improvement in recall between trials did not differ across groups. After a delay, moderate and severe groups recalled a lower proportion of words that they had learned earlier than did the control or mild groups. Across learning trials, head injured groups used semantic clustering less than controls, but after equating groups in terms of the number of possible clustered responses the mild and moderate did not differ from severe or control groups. After a delay, the severe group used semantic clustering less than the control, mild and moderate groups. The severe group showed a significantly higher proportion of intrusions than controls after a delay. All groups were affected by proactive interference. On the WMS, head injured groups demonstrated a lower MQ than controls. On the Logical Memory subtest, moderate and severe groups recalled fewer idea units than controls. All groups showed sensitivity to the semantic structure of prose passages. X Results of the present study confirm earlier findings that severely head injured patients demonstrate globally impaired memory functioning. The severely head injured group showed impairments in learning and memory across both quantitative and qualitative measures, demonstrating a less effective learning strategy. Although mild head injured subjects learned information at a lower rate than the controls, their ability to retain and retrieve information learned was not significantly impaired. The pattern of clustering responses observed across trials indicated that the severe group was unable to actively organize their memory trace, but the mild group more actively organized information