Poster #18 - Infant resting-state connectivity of inferior frontal gyrus is associated with linguistic environment

• In Event: 2-110 - Poster Session 07
  In Poster Session: PS 07 Section - Biological Processes: Neuroscience and Genetics

Integrative Statement

Introduction:
Although the neural correlates of language processing in adults are well understood, the biological basis of language acquisition—and the mechanism by which language develops—remain highly contested (Dehaene-Lambertz & Spelke, 2015). Both the left and right inferior frontal gyrus (IFG) have been shown to be important neural regions for language comprehension and production in adults (Siebner et. al., 2010). Infancy is a sensitive period for language development during which windows of neural plasticity for linguistic perception may be especially affected by variations in the environment (Werker & Hensch, 2015); we know little, however, about the role that the family language environment plays in infants’ neurobiological development. In the present study we used resting-state fMRI to examine the association between infants’ functional connectivity of the IFG and naturalistic measurements of their home linguistic environments. Based on evidence that the language environment affects brain development (Romero et al., 2018), we hypothesized that enriched linguistic environments would be associated with greater IFG connectivity with other regions implicated in language processing.

Methods:
Eighty-four socioeconomically diverse 6-month-old infants (Mean[SD] age=6.76[0.53] months) and their mothers completed at least one day of recording of the infants’ family linguistic environment using the wearable LENA device (Weisleder & Fernald, 2013). We derived hourly rates of infant exposure to adult word count (AWC), conversational turns (CTs), and infant vocalizations. Infants completed a resting-state fMRI scan during natural sleep. Data collection and processing is ongoing; currently, we have processed resting-state data from 19 infants (Mean[SD] age=6.99[0.63] months) using standard protocols adjusted appropriately for infant brains. We computed whole-brain seed-based functional connectivity estimates of manually defined bilateral IFG regions of interests, with infant age as a covariate.

Results:
Linguistic measurements were largely interrelated: AWs were associated with CTs (r(82)=.631), and CTs were associated with infant vocalizations (r(82)=.797); though AWs were unrelated to infant vocalizations (r(82)=.151). Clusters of functional activation (FWER p<.01) were identified between bilateral IFG and several brain regions. Given the limited sample size, we report the largest effects of language. Greater exposure to AWC was negatively associated with connectivity between the left IFG and the left precentral gyrus (r(17)=-.372, 95%CI [-.707, .099]; Figure 1). Greater exposure to CTs and greater frequency of infant vocalizations were negatively associated with connectivity between the right IFG and the left posterior cingulate cortex (Vocalizations: r(17)=-.430, 95%CI[-.739, .029]), the left temporal pole (Vocalizations: r(17)=-.370, 95%CI [-.705, .102]); the right superior frontal gyrus (Vocalizations: r(17)=-.339, 95%CI [-.687 - .136]), and the right precuneus (CTs: r(17)=-.304, 95%CI [-.667, .173]; Figure 2).

Discussion:
Our findings suggest that variation in the early linguistic environment may be associated with functional connectivity of the bilateral IFG in infancy. Contrary to expectations, we found that infants who experienced more linguistic interaction tended to evidence reduced functional connectivity during sleep between the IFG and other regions associated with language processing. Given the scarcity of research in this area, future analyses will focus on characterizing the association between variation in the linguistic environment and language networks in a larger sample of infants.

Authors

• Lucinda M Sisk, Stanford University
  Presenting Author

• Lucy S. King, Stanford University, Department of Psychology
  Non-Presenting Author

• M. Catalina Camacho, University of Pittsburgh
  Non-Presenting Author

• Monica E. Ellwood-Lowe, University of California, Berkeley
  Non-Presenting Author

• Kathryn Humphreys, Vanderbilt University
  Non-Presenting Author

• Ian H. Gotlib, Stanford University, Department of Psychology
  Non-Presenting Author