Language acquisition in premature and full-term infants

Abstract

We tested healthy preterm (born near 28 ± 2 weeks of gestational age) and full-term infants at various different ages. We compared the two populations on the development of a language acquisition landmark, namely, the ability to distinguish the native language from a rhythmically similar one. This ability is attained 4 months after birth in healthy full-term infants. We measured the induced gamma-band power associated with passive listening to (i) the infants' native language (Spanish), (ii) a rhythmically close language (Italian), and (iii) a rhythmically distant language (Japanese) as a marker of gains in language discrimination. Preterm and full-term infants were matched for neural maturation and duration of exposure to broadcast speech. We found that both full-term and preterm infants only display a response to native speech near 6 months after their term age. Neural maturation seems to constrain advances in speech discrimination at early stages of language acquisition.gamma-band oscillations | preterm infant | speech | rhythm | development H ow much do healthy immature brains gain from exposure to broadcast speech? Unfortunately, very few studies have investigated the interaction between experience and brain maturation in healthy premature infants during the early stages of cognitive development (1). Highly premature infants whose nervous system is immature are confronted with a wide range of external stimulation with unknown consequences on cognitive development. Here, we explore the neural correlate of a landmark of language acquisition, namely, the discrimination of the maternal language from rhythmically similar languages (2).A fair number of behavioral studies have demonstrated that fetuses and neonates distinguish utterances of languages belonging to different rhythmic classes. Indeed, in a recent study, speech perception was examined in 104 low-risk fetuses at 33-41 weeks of gestational age using a familiarization/novelty paradigm (3). One of the experiments shows that fetuses of English-speaking mothers discriminate English from Mandarin, two languages that are very different in rhythm. Moreover, other studies with 2-to 4-day-old neonates and a larger set of language pairs show different responses depending on whether the utterances belong to the same or two different rhythmic classes (2, 4, 5). In other words, once neonates become habituated to utterances of a given language, they show an increase in their nonnutritive sucking rate only when they are exposed to utterances of languages that belong to a different rhythmic class. However, at this age, neonates do not distinguish a switch that occurs between two languages that belong to the same rhythmic class. Other studies have established that it is only after 4 months that full-term infants are able to distinguish utterances in their native language from those of a language that belongs to the same rhythmic class (6, 7). How does this ability develop in healthy highly premature infants? Would preterm infants exposed to their native language for nea...

Predicting Individual Variation in Language From Infant Speech Perception Measures

“…To begin with, Peña and colleagues argue that preterms and full terms achieve the same landmarks when matched for gestational (i.e., maturational) age. In support of this conclusion, they report no difference between preterms and full terms when age has been corrected in terms of electrophysiological correlates of language discrimination (between different rhythmic classes at 3 months, and within the same class at 6 months; Peña, Pittaluga, & Mehler, 2010) and sound discrimination (native [ba-da] does not differ from nonnative [da-ɖa] at 9 months, but it does at 12 months; Peña, Werker, & Dehaene-Lambertz, 2012). The former result had also been obtained using behavioral methods in an independent lab (Bosch, 2011).…”

Effect of maturation on suprasegmental speech processing in full- and preterm infants: A mismatch negativity study

“…However, further explanations are also possible for the developmental lag of processing syllabic stress shown by preterm infants. Pena et al (2010) measuring induced gamma band power argue for example for a maturational fallback in the prosodic processing. Gimenez et al (2008) argue for causal relationship between the maturational lag and the microstructural deviations of white matter even in preterm infants without organic deficits.…”

“…Key, Lambert, Aschner, and Maitre (2012) revealed that the first 4 months of extra-uterine life represent the most sensitive period considering maturational differences in vowel and consonant discrimination. However, it has been found that in case of prosodic information preterm infants are not merely unable to profit from the experience of the longer extra-uterine life, but systematically show developmental lag (Pena, Pittaluga, & Mehler, 2010). Their results revealed, that 6 month-old preterm infants were at the level of 3 months during the discrimination of their mother tongue from a rhythmically similar language.…”

Earlier Speech Exposure Does Not Accelerate Speech Acquisition

“…Vocalization amount positively correlates with exposure to parental talk in preterms (Caskey et al, 2011), but it is unclear whether preterms are able to extract linguistic regularities from the speech input. A recent study showed that discrimination of languages from the same rhythmic class-which takes place at ϳ4.5 months in full-term infants-was not accelerated in healthy preterm infants (Peña et al, 2010). However, it can be argued that preterms have no advantage over full-terms in rhythm tasks because filtering by human tissues only weakly degrades speech rhythmic properties.…”