Logopenic variant primary progressive aphasia is a neurodegenerative language disorder primarily characterized by impaired phonological processing. Sentence repetition and comprehension deficits are observed in lvPPA and linked to impaired phonological working memory, but recent evidence also implicates impaired speech perception. Currently, neural encoding of the speech envelope, which forms the scaffolding for perception, is not clearly understood in lvPPA. We leveraged recent analytical advances in electrophysiology to examine speech envelope encoding in lvPPA. We assessed cortical tracking of the speech envelope (...) and in-task comprehension of two spoken narratives in individuals with lvPPA and age-matched controls. Despite markedly reduced narrative comprehension relative to controls, individuals with lvPPA had increased cortical tracking of the speech envelope in theta oscillations, which track low-level features, but not delta oscillations, which track speech units that unfold across a longer time scale. This neural signature was highly correlated across narratives. Results indicate an increased reliance on acoustic cues during speech encoding. This may reflect inefficient encoding of bottom-up speech cues, likely as a consequence of dysfunctional temporoparietal cortex. (shrink)

The sensitive period for phonetic learning, evidenced by improved native speech processing and declined non-native speech processing, represents an early milestone in language acquisition. We examined the extent that sensory encoding of speech is altered by experience during this period by testing two hypotheses: early sensory encoding of non-native speech declines as infants gain native-language experience, and music intervention reverses this decline. We longitudinally measured the frequency-following response, a robust indicator of early sensory encoding along the auditory pathway, to a (...) Mandarin lexical tone in 7- and 11-months-old monolingual English-learning infants. Infants received either no intervention or music intervention randomly between FFR recordings. The language-experience group exhibited the expected decline in FFR pitch-tracking accuracy to the Mandarin tone, while the music-intervention group did not. Our results support both hypotheses and demonstrate that both language and music experiences alter infants’ speech encoding. (shrink)