The concept of regularization: Resolving the problem of surface dyslexia in semantic variant primary progressive aphasia across different languages.

Surface dyslexia, a diagnostic feature of the semantic variant of primary progressive aphasia (svPPA), is difficult to observe in many languages. It can be conceptualized as one manifestation of a more general "regularization" effect-that is, with semantic impairment, patients fail to recognize exceptions and revert to default rules. OBJECTIVE: We predicted that, analogous to surface dyslexia in English, German patients with svPPA would regularize irregular verbs, especially those of lower frequency and in the less frequently used preterite tense. METHOD: Regularization was investigated in German through past-tense verb inflectional morphology in N = 10 svPPA, N = 5 PPA related to Alzheimer pathology (Aß+PPA), N = 5 patients with nonfluent variant PPA (nfvPPA), N = 12 typical (amnestic presentation) Alzheimer's disease (AD), and N = 32 healthy controls. The task involved perfect- and preterite-tense inflection of regular and irregular verbs of high and low frequency. RESULTS: Errors in svPPA particularly involved regularization (e.g., I swim → I swimmed, I have swimmed), whereas Aß+PPA made a wide range of other errors (e.g., verb agreement or tense errors). Regularization was rare in AD and controls, whereas the expected frequency effects (low worse than high) were found in svPPA. nfvPPA had profound difficulties in inflecting verbs in general. CONCLUSION: The study illustrates how tests tailored to a specific language can reveal the regularization effect of svPPA. For more universal diagnostic recommendations, future revisions for svPPA should consider substituting the criterion of surface dyslexia for that of a general criterion of regularization of language rules, the former being an example of the latter. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

The atrophy pattern in Alzheimer-related PPA is more widespread than that of the frontotemporal lobar degeneration associated variants.

OBJECTIVE: The three recognized variants of primary progressive aphasia (PPA) are associated with different loci of degeneration-left posterior perisylvian in logopenic variant (lvPPA), left frontal operculum in non-fluent variant (nfvPPA), and left rostroventral-temporal in semantic variant (svPPA). Meanwhile, it has become apparent that patients with lvPPA, in which Alzheimer pathology is the norm, frequently have more extensive language deficits-namely semantic and grammatical problems-than is captured in the strict diagnostic recommendations for this variant. We hypothesized that this may be because the degeneration in AD-related PPA typically extends beyond the left posterior perisylvian region. METHODS: Magnetic resonance images from 25 PPA patients (9AD-related PPA, 10 svPPA, 6 nfvPPA) and a healthy control cohort were used to calculate cortical thickness in three regions of interest (ROIs). The three ROIs being the left-hemispheric loci of maximal reported degeneration for each of the three variants of PPA. RESULTS: Consistent with past studies, the most severe cortical thinning was in the posterior perisylvian ROI in AD-related PPA; the ventral temporal ROI in svPPA; and the frontal opercular ROI in nfvPPA. Significant cortical thinning in AD-related PPA, however, was evident in all three ROIs. In contrast, thinning in svPPA and nfvPPA was largely restricted to their known peak loci of degeneration. CONCLUSIONS: Although cortical degeneration in AD-related PPA is maximal in the left posterior perisylvian region, it extends more diffusely throughout the left hemisphere language network offering a plausible explanation for why the linguistic profile of lvPPA so often includes additional semantic and grammatic deficits.