Specific semantic memory loss after hypoxic-ischemic injury.

Abstract

A patient is reported who suffered hypoxic-ischemic injury causing isolated and eventually partially reversible semantic memory loss. Despite normal MRI findings, single-photon emission CT demonstrated dysfunction in posterior cortical association areas. Semantic memory is the sum of categorical, perceptual, and conceptual knowledge. While not localized in a strict sense like visual fields, semantic memory is thought to be broadly organized in the posterior association cortices, with a particular focus in the inferior temporal regions. Evidence for this has come from patients with herpes simplex encephalitis, temporo-occipital infarctions, and dementias. This case confirms the importance of these cortical regions for semantic memory. The rapid recovery in this case, as opposed to the encephalitis or infarction cases, suggests an important role for preservation of white matter connections in the region for reconstitution of function.