Preservation of lexical-semantic knowledge of adjectives in the semantic variant of primary progressive aphasia: Implications for theoretical models of semantic memory

• Adjectives refer to concrete and abstract properties denoted by nouns.
• We explored the comprehension of adjectives in semantic variant of primary progressive aphasia.
• Participants were unimpaired on tasks probing knowledge about adjectives per se.
• They were impaired when asked to associate the same adjectives with object nouns.
• These results could be explained by atrophy of the anterior temporal lobes.

Adjectives are lexical words used to modify nouns and refer to physical and concrete properties as well as abstract properties denoted by nouns. Although adjectives directly refer to semantic attributes, no study has explicitly examined the comprehension of adjectives in the semantic variant of primary progressive aphasia (svPPA). In this study, we explored the comprehension of adjectival meaning in four participants with svPPA using two experimental designs assessing the comprehension of adjectives per se and the comprehension of adjectives when associated with concrete nouns. We found evidence that participants: a) were unimpaired on tasks probing knowledge about adjectives referring to dimension and physical properties, to human propensity and value, and to color, but b) showed substantial difficulty when asked to associate the same adjectives with object nouns. These results raise important questions about the lexical-semantic representation of adjectives and, more generally, about the organization of words in the lexical-semantic system. The observed difficulties could be due to the impairment in binding different modality-specific properties and combining verbal conceptual knowledge, after anterior temporal lobe atrophy.