The pattern of phonological, semantic, and circumlocution naming errors for nouns and verbs in primary progressive aphasia

Background: In the diagnostic criteria for lvPPA (Gorno-Tempini et al. 2011), “speech (phonologic) errors in spontaneous speech and naming” is a secondary criterion, but studies of naming error patterns in PPA have not found evidence to support this criterion. Furthermore, only a few studies have examined naming error patterns in PPA. Aims: In the current study, we examined the pattern of naming errors for nouns and verbs in all three subtypes of PPA, as well as unclassifiable PPA and typical (amnestic) Alzheimer’s disease (AD). Statistical analyses focused on three common error types: phonological, semantic, and circumlocution errors. Methods & Procedures: The final sample included 35 participants with PPA and four participants with typical AD. Participants were asked to name 284 noun pictures and 116 verb pictures. Separately for nouns and verbs, repeated-measures ANCOVA was used to examine the interaction between Error Type and Diagnostic Subtype. Twenty of the participants also completed a structural MRI scan. For these participants, we examined the relationships between naming errors and brain volume within ten left hemisphere regions of interest (ROIs). Outcomes & Results: In lvPPA, the proportion of phonological errors was significantly lower than the proportion of semantic errors for verbs. In svPPA, uPPA, and typical AD, semantic errors were significantly greater than phonological errors for both nouns and verbs. In between-subtype analyses, the proportion of semantic errors for nouns was significantly greater for participants with svPPA and uPPA, compared to those with nfvPPA. For nouns, the MRI analyses revealed significant negative correlations between the proportion of circumlocution errors and volume in the left inferior temporal gyrus and the left fusiform gyrus. For verbs, there were significant negative correlations between circumlocution errors and volume in the left insula, and between semantic errors and volume in the left superior temporal pole. Conclusions: The findings of this study indicate that semantic naming errors may be common for both nouns and verbs in typical AD and all subtypes of PPA, with the possible exception of nouns in nfvPPA. In contrast, phonological naming errors were not significantly more common than semantic errors in any diagnostic subtype. Furthermore, phonological naming errors were not significantly more common in lvPPA, compared to any other diagnostic subtype.