Infant Language Exposure Shapes Brain Circuitry

Summary: Taking turns in “conversations” with adult caregivers synchronizes activity in language areas of the infant brain.

Source: SfN

The type and quantity of an infant’s language exposure relates to their brain function, according to new research published in Journal of Neuroscience.

Babies learn their native language by interacting with their caregivers. Rather than simply overhearing adult words, taking turns in a “conversation” predicts an infant’s future language abilities. But it is unclear how language exposure shapes brain circuitry.

The brain’s language networks may develop in two stages: a bottom-up auditory-processing network begins developing in gestation, and a top-down network for processing more complex syntax and semantics develops in early childhood.

King et al. documented the at-home language exposure of 5 to 8-month-old infants and used fMRI to measure their resting language network activity while they slept in the scanner. Regions in each of the two language subnetworks activated together, indicating coordinated activity. Participating in a greater number of conversational turns at home was associated with weaker connectivity in the bottom-up subnetwork.

This shows a baby
An infant wears the LENA audio recording device in a pocket on the front of a special vest. Credit: Dr. Kathryn L. Humphreys

Brain connections can both weaken and strengthen as they are refined throughout development; future research may reveal how weaker connectivity related to more conversations influences infant language development.

Regardless, the results highlight the importance of early life environments in shaping infant brain function and development, and the need to support caregivers in providing enriching environments.

About this language research news

Source: SfN
Contact: Calli McMurray – SfN
Image: The image is credited to Dr. Kathryn L. Humphreys

Original Research: Closed access.
Naturalistic Language Input is Associated with Resting-State Functional Connectivity in Infancy” by Kathryn L. Humphreys et al. Journal of Neuroscience


Naturalistic Language Input is Associated with Resting-State Functional Connectivity in Infancy

The quantity and quality of the language input that infants receive from their caregivers affects their future language abilities; however, it is unclear how variation in this input relates to preverbal brain circuitry. The current study investigated the relation between naturalistic language input and the functional connectivity of language networks in human infancy using resting-state functional magnetic resonance imaging (rsfMRI). We recorded the naturalistic language environments of 5- to 8-month-old male and female infants using the Linguistic Environment Analysis (LENA) system and measured the quantity and consistency of their exposure to adult words and adult–infant conversational turns. Infants completed an rsfMRI scan during natural sleep and we examined functional connectivity among regions of interest previously implicated in language comprehension, including the auditory cortex, the left inferior frontal gyrus (IFG), and the bilateral superior temporal gyrus (STG). Consistent with theory of the ontogeny of the cortical language network (Skeide and Friederici, 2016), we identified two subnetworks posited to have distinct developmental trajectories: a posterior temporal network involving connections of the auditory cortex and bilateral STG and a frontotemporal network involving connections of the left IFG. Independent of socioeconomic status, the quantity of conversational turns was uniquely associated with functional connectivity of these networks. Infants who engaged in a larger number of conversational turns in daily life had lower connectivity in the posterior temporal language network. These results provide evidence for the role of vocal interactions with caregivers, compared to overheard adult speech, in the function of language networks in infancy.


Infants whose caregivers speak to them more develop better language skills. It is unclear, however, how real-word language input is associated with preverbal brain circuitry. Resting-state functional magnetic resonance imaging during natural sleep can noninvasively measure patterns of brain activation in infancy. The present study finds that the quantity of vocal interactions infants engage in with their caregivers in daily life correlates with the strength of resting-state functional connectivity in regions of the brain implicated in language comprehension. These results provide evidence for the role of vocal interactions with caregivers in the function of language networks in infancy. Interventions that focus on increasing vocal interactions may be associated with infant brain function in a manner that ultimately enhances language abilities.

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