Biology subjects

Perez-Navarro, J.

Publications and source records attributed to Perez-Navarro, J..

3 recordsLinked to original sources

bioRxiv2026

The cortex encodes speech timing as departure from expectation, not as physical measurement

Every syllable and every phoneme in natural speech has a different duration. This variability is conventionally treated as jitter, noise the brain must overcome to recover an underlying regularity. Here we show that the cortex encodes it as information. We recorded magnetoencephalography from 25 native listeners of Spanish during twenty minutes of spontaneous narrative speech in Spanish, a syllable-timed language in which durational variability is low, making it a conservative test case. We modelled cortical activity with three timing regressors defined at successively finer grains: deviation from the expected syllabic beat, from the expected phoneme onset, and from the expected duration of the phoneme just completed. Fitted jointly, and against acoustic and linguistic-surprisal baselines, each regressor explained unique activity in bilateral superior temporal cortex, with distinct response latencies spanning 70 to 250 ms. The duration regressor explained cortical activity beyond raw phoneme duration, whereas raw duration explained no additional variance once it was included. At the onset grain, by contrast, predicted and physical timing contributed jointly. The onset departure was encoded with its sign, distinguishing events that arrived early from those that arrived late. In a separate sample, removing this durational variability was costly: comprehension in noise degraded under imposed isochrony relative to natural timing. Durational variability is therefore not noise the cortex discards but information it encodes, across a hierarchy of timescales - and at the finest grain, what is encoded is not how long a speech event lasted but how far its duration departed from expectation.

neuroscience↗

bioRxiv2024

Are you talking to me? How the choice of speech register impacts listeners' hierarchical encoding of speech.

Speakers accommodate their speech to meet the needs of their listeners, producing different speech registers. One such register is Foreigner-Directed Speech (FDS), which is the way native speakers address non-native listeners, typically characterized by features such as slow speech rate and phonetic exaggeration. Here, we investigated how register impacts the cortical encoding of speech at different levels of language integration. Specifically, we tested the hypothesis that enhanced comprehension of FDS compared with Native-Directed Speech (NDS) involves more than just a slower speech rate, influencing speech processing from acoustic to semantic levels. Electroencephalography (EEG) signals were recorded from Spanish native listeners, who were learning English (L2 learners), and English native listeners (L1 listeners) as they were presented with audio-stories. Speech was presented in English in three different speech registers: FDS, NDS and a control register (Slow-NDS) which is slowed down version of NDS. We measured the cortical tracking of acoustic, phonological, and semantic information with a multivariate temporal response function analysis (TRF) on the EEG signals. We found that FDS promoted L2 learners cortical encoding at all the levels of speech and language processing considered. First, FDS led to a more pronounced encoding of the speech envelope. Second, phonological encoding was more refined when listening to FDS, with phoneme perception getting closer to that of L1 listeners. Finally, FDS also enhanced the TRF- N400, a neural signature of lexical expectations. Conversely FDS impacted acoustic but not linguistic speech encoding in L1 listeners. Taken together, these results support our hypothesis that FDS accommodates speech processing in L2 listeners beyond what can be achieved by simply speaking slowly, impacting the cortical encoding of sound and language at different abstraction levels. In turn, this study provides objective metrics that are sensitive to the impact of register on the hierarchical encoding of speech, which could be extended to other registers and cohorts.

neuroscience↗

bioRxiv2023

The contribution of early language exposure to the cortical tracking of speech

Cortical tracking of speech is relevant for the development of speech perception skills. However, no study to date has explored whether and how cortical tracking of speech is shaped by accumulated language experience, the central question of this study. In 35 bilingual children (6 y.o.) with considerably bigger experience in one language, we collected electroencephalography data while they listened to continuous speech in their two languages. Cortical tracking of speech was assessed at acoustic-temporal and lexico-semantic levels. Children showed more robust acoustic-temporal tracking in the least experienced language, and more sensitive cortical tracking of semantic information in the most experienced language. Additionally, and only for the most experienced language, acoustic-temporal tracking was specifically linked to phonological abilities, and lexico-semantic tracking to vocabulary knowledge. Our results indicate that accumulated linguistic experience is a relevant maturational factor for the cortical tracking of speech at different levels during early language acquisition.

neuroscience↗