Distinguishing Among Variants of Primary Progressive Aphasia with a Brief Multimodal Test of Nouns and Verbs

Primary Progressive Aphasia (PPA) variants include the non-fluent agrammatic (nfvPPA), logopenic (lvPPA), and semantic (svPPA), which differ in their effects on speech production. However, their impact on modality (oral vs. written) and grammatical word class (nouns vs. verbs) remains controversial. A significant effect of these variables might assist in classification.

This study used first-visit data from 300 participants with PPA who completed oral and written noun and verb naming (matched in surface word frequency across word class) to test the hypothesis that the three variants show differential impairment on word class or modality. Group differences were evaluated with rank-transformed repeated measures ANOVA. Within individual differences between nouns and verbs and between oral and written modalities were tested with Fisher's exact tests.

A significant modality × variant interaction (p = 0.017) was observed. Participants with lvPPA and nfvPPA demonstrated greater oral than written naming, with nfvPPA also performing better on nouns than verbs. Those with svPPA showed no modality or word class effects but had an overall low accuracy. Three participants with svPPA (but no individuals with the other variants) demonstrated significantly (p = 0.003) more accurate verb than noun naming.

Differing modality and word class patterns characterize PPA variants, with nfvPPA more accurate in nouns than verbs on average. Within individuals, only those with svPPA occasionally showed significantly more proficient verb than noun naming. Grammatical word class effects likely arise at distinct levels of cognitive processing underlying naming.