Reversal of the concreteness effect in a patient with semantic dementia

Normal subjects are better at identifying and remembering concrete as compared to abstract words (the concreteness effect). We present data on a patient, DM, who shows the opposite pattern. DM has a progressive semantic loss due to atrophic changes in his temporal lobes, particularly on the left. His semantic impairment predominantly involves object terms, with relative sparing of abstract nouns and most aspects of verb meaning. DM showed an advantage for abstract words on a wide range of tasks (e.g. producing definitions, synonymy judgments). These data challenge accounts that attribute the concreteness effect to a quantitative superiority at the level of the underlying conceptual representations. We suggest that there are qualitative differences between abstract and concrete concepts, and that, in particular, concrete concepts are more dependent on perceptual attributes that were disproportionately impaired in DM. We propose, further, that perceptual components of semantic representations are associated with structures in the inferior temporal lobe(s).