Where does the "ἀφημί" (speechless) in nfvPPA come from?: a case study on phonological retrieval and the potent...

Diagnosing non-fluent/agrammatic variant primary progressive aphasia (nfvPPA) relies primarily on apraxia of speech (AOS) and agrammatism. However, differentiating phonetic-level (articulatory) from phonemic-level (phonological) impairments remains clinically challenging, especially in advanced stages. We report a 65-year-old Japanese male with nfvPPA who had become virtually speechless (ἀφημί). Leveraging the Kana writing system's one-to-one correspondence to morae, we designed a cross-modal experiment to isolate his underlying deficit. Speech production was evaluated across four conditions: picture naming, Kanji word reading, Kana word reading, and character-by-character Kana reading. Statistical analysis was performed using Fisher's exact test and adjusted residual analysis. Speech intelligibility significantly improved during character-by-character Kana reading compared to other modalities. Residual analysis confirmed that explicit moraic cues markedly reduced error rates. These findings indicate that our approach effectively unmasked superimposed phonemic-level retrieval deficits contributing to speechlessness in nfvPPA. This study highlights the utility of Japanese orthography in disentangling underlying mechanisms and demonstrates that moraic assistance can serve as a potent facilitation strategy in severe cases.