Countries: Their selective impairment and selective preservation

We present two cases that argue for a further fractionation of semantic knowledge in the category of proper names. In both patients the provisional diagnosis was progressive dementia, Alzheimer's (patient DK) and Pick's (patient TM) respectively. Patient DK was selectively impaired in naming and comprehending countries within the visual modality. Thus, he was unable to name a country from its map or to point to it on the map from its spoken name, whilst being able to name that same country promptly from verbal description. His naming and comprehension were intact for famous people's names and for all other categories of knowledge tested. By contrast, patient TM's naming and comprehension of people's names and all categories except for countries were profoundly impaired. We show that his impairment is limited to the verbal modality. We conclude that the observed category by modality interaction can be accommodated best by the multiple semantics hypothesis. Thus, countries are selectively impaired within DK's visual semantics and people are selectively impaired within TM's verbal semantics.