The impact of phonological short-term memory impairment on verbal repetition in the logopenic variant of primary progressive aphasia

The Functional Origin of Oral Word Production Deficits in the Logopenic Variant of Primary Progressive Aphasia: A Systematic Review

BACKGROUND/OBJECTIVES

Oral word production (OWP) deficits are prominent in the logopenic variant of primary progressive aphasia (lvPPA); however, their functional origin remains unclear. Some studies suggest a lexical, post-lexical, or even a combined functional origin of these deficits. The aim of the present study was to synthesize and analyze the information on the functional origin of the OWP deficits in patients with lvPPA.

METHODS

A quantitative systematic literature review was carried out using four databases: CINAHL, PsycINFO, Linguistics and Language Behavior Abstracts, and PubMed. Fourteen studies, including a total of 243 patients with lvPPA, and reporting results on picture naming and/or word and/or pseudoword repetition, were selected.

RESULTS

The overall findings of this review highlighted that two main functional origins appear to explain the OWP deficits in lvPPA: a lexical impairment affecting lexical processing and a post-lexical impairment affecting phonological short-term memory. Interestingly, the possibility of a third functional origin, affecting the semantic processing level, was also suggested by some studies.

CONCLUSIONS

We concluded that the presence of different functional origins of OWP in this population may be explained, at least partially, by the diversity of assessment tasks used in studies and the varied manipulation and control of psycholinguistic properties of words (e.g., frequency, length), as well as the various interpretations and analyses of the participants' errors. Further studies are needed to substantiate these findings by examining all the components involved in OWP, carefully manipulating the psycholinguistic properties and qualitatively analyzing the errors made by lvPPA participants.

The Classification and Language Description of Patients with Primary Progressive Aphasia Using the Mini Linguistic State Examination Test

Introduction. Primary progressive aphasia (PPA) is a clinical syndrome characterized by a progressive deterioration in language and speech. It is classified into three variants based on symptom patterns: logopenic, semantic, and non-fluent. Due to the lack of fully reliable and valid screening tests for diagnosing PPA and its variants, a Spanish version of the Mini Linguistic State Examination (MLSE) has recently been introduced. Materials and methods. This study aimed to describe the language impairments in a small sample of six patients with PPA and classify them into the three variants using the decision tree and syndrome guide proposed by the MLSE authors. Results. The findings demonstrate the test's utility in classifying some PPA variants through a qualitative analysis of patient performance and error types. The study revealed a 50% accuracy rate for the decision tree and an 83.33% accuracy rate when using the syndrome guide. Discussion. This discrepancy arises because the decision tree often classified cases as logopenic variant PPA (lvPPA) when working memory was significantly impaired. Specifically, it tended to misclassify patients with semantic, motor, or speech impairments as having lvPPA due to its reliance on the sentence repetition task for assessing working memory.

Heterogeneity and overlap in the continuum of linguistic profile of logopenic and semantic variants of primary progressive aphasia: a Profile Analysis based on Multidimensional Scaling study

BACKGROUND

Primary progressive aphasia (PPA) diagnostic criteria underestimate the complex presentation of semantic (sv) and logopenic (lv) variants, in which symptoms partially overlap, and mixed clinical presentation (mixed-PPA) and heterogenous profile (lvPPA +) are frequent. Conceptualization of similarities and differences of these clinical conditions is still scarce.

METHODS

Lexical, semantic, phonological, and working memory errors from nine language tasks of sixty-seven PPA were analyzed using Profile Analysis based on Multidimensional Scaling, which allowed us to create a distributed representation of patients' linguistic performance in a shared space. Patients had been studied with [18F] FDG-PET. Correlations were performed between metabolic and behavioral data.

RESULTS

Patients' profiles were distributed across a continuum. All PPA, but two, presented a lexical retrieval impairment, in terms of reduced production of verbs and nouns. svPPA patients occupied a fairly clumped space along the continuum, showing a preponderant semantic deficit, which correlated to fusiform gyrus hypometabolism, while only few presented working memory deficits. Adjacently, lvPPA + presented a semantic impairment combined with phonological deficits, which correlated with metabolism in the anterior fusiform gyrus and posterior middle temporal gyrus. Starting from the shared phonological deficit side, a large portion of the space was occupied by all lvPPA, showing a combination of phonological, lexical, and working memory deficits, with the latter correlating with posterior temporo-parietal hypometabolism. Mixed PPA did not show unique profile, distributing across the space.

DISCUSSION

Different clinical PPA entities exist but overlaps are frequent. Identifying shared and unique clinical markers is critical for research and clinical practice. Further research is needed to identify the role of genetic and pathological factors in such distribution, including also higher sample size of less represented groups.