Babies born to bilingual mothers who were exposed to two languages in the uterus exhibit different brain responses to speech-like sounds at just a few days old compared with those born to monolingual mothers, further suggesting the influence of prenatal experiences on language acquisition.
Newborns have a over non-speech sounds and can based on their rhythms. Previous research has shown that 4-month-old babies living in bilingual homes have distinct patterns of brain activity, but it was unclear how prenatal exposure to more than one language affects much younger infants鈥� brain responses to speech.
To investigate, at the University of Barcelona in Spain and her colleagues recruited 131 full-term babies aged between 1 and 3 days old, 53 of whom had mothers who spoke only Spanish and 78 of whom had mothers who spoke both Spanish and Catalan.
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They played the babies a series of 鈥渙a鈥� sounds for a quarter of a second each, while scalp electrodes recorded their frequency-following responses, a marker of brain activity that reflects the efficiency with which speech sounds are processed. These are generated by the synchronised activity of neurons in the brain鈥檚 auditory processing pathway and are known to be disrupted in a range of speech and language conditions.
The researchers found that the babies born to bilingual mothers exhibited a lower so-called signal-to-noise ratio in response to each sound compared with those born to monolingual mothers. This measures the strength of the desired sound signal relative to any background noise, with a lower ratio indicating better-quality neural patterns.
Bilingual speech contains more complex sound signals than monolingual speech, so babies born to mothers who speak more than one language are more sensitive to speech frequencies, the researchers write in their paper.
There were no differences among the babies within either the bilingual or monolingual groups, which suggests that their distinct brainwave patterns were the result of their language exposure in the uterus, rather than what they heard in the first few days of life.
鈥淭his highlights how exposure to multiple languages during pregnancy affects the neural encoding of speech sounds at birth and serves as compelling evidence of the intricate role prenatal experiences play in shaping early language acquisition,鈥� says at Oxford Brookes University in the UK.
This builds on previous research that shows babies may start to learn language before they are born and emphasises the potentially vast cognitive abilities that fetuses are capable of, she says. Studying this helps us better understand the beginnings of language acquisition, which may be affected in premature babies if it starts in the uterus, says Gonzalez-Gomez.
bioRxiv
