Introduction: Primary Progressive Aphasia (PPA) is a neurodegenerative syndrome characterized by a progressive and predominant impairment of language functions. Among its variants, the logopenic variant (lvPPA) is distinguished by marked deficits in auditory-verbal short term memory (avSTM), leading to impaired sentence and phrase repetition. This impairment reflects dysfunction of the phonological loop and constitutes a core diagnostic feature of lvPPA¹. This study investigates the relationship between language performance and cortical thickness in lvPPA using structural MRI. 

Methods: Twenty-eight participants were included:14 individuals with lvPPA and 14 healthy controls. Groups were matched for age and sex; years of education differed between groups and were therefore included as a covariate in all analyses. Structural MRI data were processed using the CAT12.9 (r2577) segmentation pipeline, and cortical thickness measures were extracted according to the Desikan Killiany atlas. All participants underwent a comprehensive neuropsychological assessment with a focus on naming and repetition abilities. Group comparisons were conducted using ANCOVA, and partial correlation analyses were performed controlling for education.

Results: Controlling for education, ANCOVA revealed a significant reduction in left superior temporal gyrus (STG) cortical thickness in lvPPA compared to controls (F(1,25)=28.01, p<0.001), with education itself acting as a significant covariate (p=0.009). This confirms independent structural alterations in the left posterior peri-Sylvian region. In the lvPPA group, partial correlations adjusted for education showed that left STG thickness positively associated with naming (r=0.524, p=0.005) and repetition (r=0.526, p=0.005) tests². Conversely, right STG thickness showed no significant language associations (p>0.05).

Conclusions: Our findings provide robust neuroanatomical evidence that focal cortical thinning in the left posterior peri Sylvian region— specifically STG and supramarginal (SMG) gyri—serves as the primary substrate for phonological loop dysfunction in lvPPA. The strong clinico anatomical correlations highlight regional cortical thickness as a reliable and objective biomarker for distinguishing lvPPA. These results reinforce the diagnostic utility of MRI-based structural metrics in clinical settings, especially for characterizing the linguistic profile of the logopenic variant.

References: [1] Gorno-Tempini, M. L., Hillis, A. E., Weintraub, S., Kertesz, A., Mendez, M., Cappa, S. F., ... & Grossman, M. (2011). Classification of primary progressive aphasia and its variants. Neurology, 76(11), 1006 1014. [2] Toğram, B., & Maviş, İ. (2012). Afazi Dil Değerlendirme Testi’nin Geçerlik, Güvenirlik ve Standardizasyon Çalışması. Turkish Journal of Neurology/Turk Noroloji Dergisi, 18(3).

Contact: didem.oz@gbhi.org This research is supported by TÜBİTAK (Project Number: 123R078)