Reversed concreteness effect for nouns in a subject with semantic dementia.

Selective sparing of abstract relative to concrete words has been documented only exceptionally in aphasia, following bilateral temporal damage. In this paper we present a new case with sparing of abstract word processing and impairment of concrete words due to selective atrophy of the left anterior temporal regions. In our subject, the reversal of the concreteness effect was restricted to nouns. Performance on nouns was not homogeneous. Proper names (people and landmarks) were very severely damaged. Among common names, living entities were selectively impaired in comparison to non-living entities. Category-specific damage for living beings resulted from widespread loss of conceptual information, and perceptual information was less impaired than associative knowledge. This observation challenges theories explaining the reversal of concreteness effect with a selective loss of perceptual information. Also the alternative account, namely a different representational architecture for abstract as opposed to concrete terms, with an advantage for concrete words accruing from an impairment of categorical information, fails to account for the data. Most subjects showing preserved knowledge of abstract words, relative to concrete words, suffer from diseases affecting anterior temporal regions (semantic dementia, herpes encephalitis), and frequently present with greater, or unilateral involvement of the left hemisphere. Our case converges with similar previous reports and with some neuroimaging studies in suggesting that the right temporal lobe and probably the left inferior prefrontal gyrus play a crucial role in the representation of abstract concepts.