Unilateral left prosopometamorphopsia: a neuropsychological case study.

We describe a patient who suddenly developed prosopometamorphopsia after a childbirth; she claimed that the left half of well-known and unfamiliar faces looked distorted. Brain MR was normal, whereas SPECT showed hypoperfusion of the left infero-lateral occipital cortex. No visual recognition defects for objects or faces were present. In three matching tasks with half-faces (Experiment 1), chimeric faces (Experiment 2), or chimeric objects (Experiment 3), the patient was impaired only when she matched pairs of chimeric faces differing in their left half; the same results were obtained after 1 year. This is the first behavioural demonstration of selective chronic metamorphopsia for the left side of faces, and provides new insights for models of face processing.