Abstracts

Discontinuity in the development of memory has been described by Vakil et al (1998) for children younger or older than 11 years of age based on a large cross-sectional study of performance on the Rey Auditory-Verbal Learning Test (AVLT), a test extensively used in epilepsy research. This discontinuity has been attributed to developmental changes in strategy utilization, planning, and conceptualization, abilities associated with maturation of the frontal lobes. In order to directly evaluate the effects of age on strategy utilization during the AVLT, the subjective organization (SO) and serial position effects (initial, middle, final) were compared for a group of children administered the AVLT prior to 11 years of age and subsequently as adolescents. AVLT performance of 20 children, 10 evaluated pre/post resection for medically intractable seizures, was scored for frequency of paired words (PF) on four blocks of successive trials, a measure of SO, and for serial positions for Trial 1 and across trials, another measure of sequential organization. Mean ages at time of initial testing and second testing were 9.4 and 15.5 years, respectively. Mean Full Scale IQ was 87.7. There were no significant differences in age or IQ for children with or without surgery. Surgical focus was 50% temporal, 33% frontal, and 17% parietal/occipital without differences in laterality. Repeated measures analyses of variance were computed on pair frequencies (Age x Surgery x Trial Block) and mean words correct for Trial 1 and across trials (Age x Serial Position). Results showed significant main effects for recall of paired words according to age (.02) and block (.01) and their interaction (.01) and for serial position in Trial 1 and across trials according to age (.001) and position (.0001). Subjective organization increased with age specifically for trials 3 to 5 and for words in the beginning and middle but not final parts of the list regardless of surgical status. Total learning (.0001) and delayed recall (.04) increased with age as expected. Relative to their preoperative performance as children, adolescents showed greater use of organizational strategies and improvement in verbal learning and recall of unrelated words as was found for adolescents who did not have surgery. Improved learning/recall was not due to changes in working memory. Rather, results support a discontinuity in the development of memory based on increased efficiency of encoding and transfer to long-term memory as a consequence of an active, effortful use of organizational strategies likely associated with prefrontal maturation. Epilepsy surgery had no negative effects on this developmental change.