Verbal Learning and Memory in Agenesis of the Corpus Callosum

The purpose of this study was to assess verbal learning and memory in individuals with agenesis of the corpus callosum (ACC) using the California Verbal Learning Test-Second Edition (CVLT-II; Delis, Kaplan, Kramer, & Ober, 2000). To assess verbal learning and memory, twenty-six individuals with Primary ACC (19 complete, 7 partial) were compared against 26 age, education, and FSIQ matched controls. Individuals with ACC and matched controls were assessed on list-learning, short and long delayed recall, and performance on Donders' (2008) four factors (i.e., Attention Span, Learning Efficiency, Delayed Memory, and Inaccurate Memory). Results showed that individuals with ACC performed significantly worse on initial list-learning (i.e., List A 1-5 Total) and on recall over the four short and long delayed recall conditions; individuals with ACC also demonstrated deficient performance on Donders' Delayed Memory factor. Deficient performances by individuals with ACC on the Delayed Memory factor was understood in terms of lateralization of encoding and retrieval processes in concert with deficits in interhemispheric transfer of information. Further, decreased access to wider cortical networks in the right hemisphere and increased reliance upon unilateral encoding of information might have led to less robust or durable memory traces.