Herpesvirus in the Hippocampus as a Cause of Alzheimer's Disease

To the Editor.  —The fascinating account by Damasio and colleagues¹ of a patient, who suffered a multimodal amnesic syndrome following bilateral temporal and basal forebrain damage from herpes simplex encephalitis, echoes a concept originally proposed in 1974 by Penfield Mathieson,² who suggested that the hippocampal formation provides the "keys of access" to a lifetime of memory stores. In that landmark article, it was suggested from surgical and autopsy data not only that the hippocampus was the anatomical substrate for "lines of facilitation" to our neocortical storage of experiential recall—what Damasio et al have phrased "the estimation of temporal and spatial relationships between separate sensory information items"—but also that there might even be an anteroposterior anatomical gradient for these connections within the hippocampus itself. Penfield and Mathieson² wondered whether the oldest memories were accessed through the more posterior portion of the hippocampal formation and the more recently stored items