The role of the left hippocampal region in the acquisition and retention of story content.

Thirteen normal control subjects and 62 patients who had undergone either a unilateral temporal or a unilateral frontal lobectomy learned the content of a short prose passage to a strict criterion. Compared to other subject, patients with left temporal-lobe excision took longer to learn the story content and, within this group, the slowest rate noted was for patients with extensive removal from the hippocampal region. When retention of the material was tested after a 20 min delay, only the group with large excisions from the left hippocampus and/or parahippocampal gyrus was impaired. This finding of abnormally rapid forgetting of material learned to criterion highlights the role of the left hippocampal region in the long-term maintenance of verbal information presented in a context.