Attenuated brain responses to speech sounds in moderate preterm infants at term age.

Recent findings have revealed that very preterm neonates already show the typical brain responses to place of articulation changes in stop consonants, but data on their sensitivity to other types of phonetic changes remain scarce. Here, we examined the impact of 7-8 weeks of extra-uterine life on the automatic processing of syllables in 20 healthy moderate preterm infants (mean gestational age at birth 33 weeks) matched in maturational age with 20 full-term neonates, thus differing in their previous auditory experience. This design allows elucidating the contribution of extra-uterine auditory experience in the immature brain on the encoding of linguistically relevant speech features. Specifically, we collected brain responses to natural CV syllables differing in three dimensions using a multi-feature mismatch paradigm, with the syllable/ba/ as the standard and three deviants: a pitch change, a vowel change to/bo/ and a consonant voice-onset time (VOT) change to/pa/. No significant between-group differences were found for pitch and consonant VOT deviants. However, moderate preterm infants showed attenuated responses to vowel deviants compared to full terms. These results suggest that moderate preterm infants' limited experience with low-pass filtered speech prenatally can hinder vowel change detection and that exposure to natural speech after birth does not seem to contribute to improve this capacity. These data are in line with recent evidence suggesting a sequential development of a hierarchical functional architecture of speech processing that is highly sensitive to early auditory experience.

Enhanced Neonatal Brain Responses To Sung Streams Predict Vocabulary Outcomes By Age 18 Months.

Words and melodies are some of the basic elements infants are able to extract early in life from the auditory input. Whether melodic cues contained in songs can facilitate word-form extraction immediately after birth remained unexplored. Here, we provided converging neural and computational evidence of the early benefit of melodies for language acquisition. Twenty-eight neonates were tested on their ability to extract word-forms from continuous flows of sung and spoken syllabic sequences. We found different brain dynamics for sung and spoken streams and observed successful detection of word-form violations in the sung condition only. Furthermore, neonatal brain responses for sung streams predicted expressive vocabulary at 18 months as demonstrated by multiple regression and cross-validation analyses. These findings suggest that early neural individual differences in prosodic speech processing might be a good indicator of later language outcomes and could be considered as a relevant factor in the development of infants' language skills.

Rapid gains in segmenting fluent speech when words match the rhythmic unit: evidence from infants acquiring syllable-timed languages.

The ability to extract word-forms from sentential contexts represents an initial step in infants' process toward lexical acquisition. By age 6 months the ability is just emerging and evidence of it is restricted to certain testing conditions. Most research has been developed with infants acquiring stress-timed languages (English, but also German and Dutch) whose rhythmic unit is not the syllable. Data from infants acquiring syllable-timed languages are still scarce and limited to French (European and Canadian), partially revealing some discrepancies with English regarding the age at which word segmentation ability emerges. Research reported here aims at broadening this cross-linguistic perspective by presenting first data on the early ability to segment monosyllabic word-forms by infants acquiring Spanish and Catalan. Three different language groups (two monolingual and one bilingual) and two different age groups (8- and 6-month-old infants) were tested using natural language and a modified version of the HPP with familiarization to passages and testing on words. Results revealed positive evidence of word segmentation in all groups at both ages, but critically, the pattern of preference differed by age. A novelty preference was obtained in the older groups, while the expected familiarity preference was only found at the younger age tested, suggesting more advanced segmentation ability with an increase in age. These results offer first evidence of an early ability for monosyllabic word segmentation in infants acquiring syllable-timed languages such as Spanish or Catalan, not previously described in the literature. Data show no impact of bilingual exposure in the emergence of this ability and results suggest rapid gains in early segmentation for words that match the rhythm unit of the native language.

Short-term experience increases infants' sensitivity to audiovisual asynchrony.

The present study explored the effects of short-term experience with audiovisual asynchronous stimuli in 6-month-old infants. Results revealed that, in contrast with adults (usually showing temporal recalibration under similar circumstances), a brief exposure to asynchrony increased infants' perceptual sensitivity to audiovisual synchrony.