Sentence repetition deficits in the logopenic variant of PPA: linguistic analysis of longitudinal and cross-sectional data

ABSTRACT

Background: The logopenic variant of primary progressive aphasia (lvPPA) is the most recently identified subtype within the primary progressive aphasia spectrum. Data characterizing this subtype based on comprehensive testing and sophisticated error analyses over time are still rare. One of the two core features of this subtype is a deficit in sentence repetition.

Aims: To provide a more fine-grained linguistic characterization of the sentence repetition deficit in lvPPA.

Methods & Procedures: We longitudinally analyzed sentence repetition abilities of eight lvPPA patients (mean age 67.6 years; two women) and a group of seven healthy controls (mean age 66.7 years; three women) using a novel schema for the classification of linguistic errors.

Outcomes & Results: At their first examination, patients with lvPPA showed an overall impaired repetition performance compared to controls with a variable degree of impairment on the first and all subsequent dates of measurement. Two patients presented with a steady, rather unimpaired profile, similar to the control group. In progression, however, five patients showed an increase of errors especially in the categories omissions and phonological errors, occasionally resulting in violation of syntactic rules.

Conclusions: These results expand existing descriptions of repetition abilities in lvPPA patients. The paper thus provides a more fine-grained classification scheme for sentence repetition performance and emphasizes the role of omissions and phonological errors in lvPPA. This, in turn, offers new insights into the linguistic nature of sentence repetition deficits in lvPPA beyond the application of mere correctness judgments.

KEYWORDS:

• PPA-L
• lvPPA
• phonology
• working memory
• aphasia

Acknowledgments

This work was supported by a JARA Seed Fund grant to SH and MG.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. For the definition of statistical outliers in the groups, we applied the definition by Tuckey (1977).

2. One patient (P02) was not able to complete the whole tests of 64 sentences. Therefore, we converted the raw values into values of relative frequency in order to ensure visual comparability among all participants. These relative frequencies are provided in all figures but were not used in statistical analysis due to the use of nonparametric methods.

3. This finding is in accordance with these patients’ good initial performance in the AAT subtest repetition (Table 2). However, testing the two patients additionally with the VLT revealed that they both performed below the first percentile, indicating an extremely low medium-term working memory capacity.

4. In particular, the close resemblance of the temporal trajectories of sentence repetition abilities (Figure 3) and digit span (Figure 8) is suggestive. Patients 05 and 07 have stable or increasing trajectories; patients 01 and 08 mostly show decline; patient 04 has a variable time course; and patients 02 and 03 whose sentence repetition abilities decrease over time already show bottom effects in their verbal working memory scores.

Additional information

Funding

This work was supported by a JARA Seed Fund grant to SH and MG.