Forgetting from long-term memory in severe closed-head injury patients: effect of retrieval conditions and semantic organization

This study was aimed at investigating long-term forgetting in chronic survivors of severe closed-head injury (CHI). For this purpose, performance decay passing from a 30-sec- to a 60-min-delay test in four memory procedures (Free Recall of unrelated stimuli, Free Recall of related stimuli. Cued Recall and y/n Recognition) of 20 CHI and 20 normal controls was analyzed. Comparable 30-sec-delay performance in CHI and control patients were obtained by manipulating exposure times to study material during the learning phase. Results demonstrated accelerated forgetting in CHI patients in the Free Recall of the related list only. This finding was particularly evident in CHI patients suffering from a focal temporal lobe lesion. These data are discussed in light of retrieval and encoding deficits characterizing memory disorders in CHI patients.