Neural development of language and speech in infants and toddlers
Poster No:
1322
Submission Type:
Abstract Submission
Authors:
Kelly Hiersche1, Zeynep Saygin1
Institutions:
1The Ohio State University, Columbus, OH
First Author:
Co-Author:
Introduction:
Children acquire language without formal instruction. The "language-ready" brain hypothesis suggests infant brains are prewired for language acquisition due to the asymmetries in anatomical regions associated with language processing (Boeckx, 2014; Dehaene-Lambertz, 2006). Testing this hypothesis requires using both structural and functional MRI in the same infant, ideally using similar rigor as neuroimaging in adults; however, because children are notoriously difficult to scan with task fMRI during these early years of language acquisition, this hypothesis has not yet been explored. How early in human development can we observe selectivity within the language network to linguistically meaningful stimuli vs. human-produced speech sounds that are not linguistically meaningful? Are the early structural asymmetries actually precursors to this neural tuning for language or speech? In this study, we leverage novel neuroimaging and analysis methods to examine the response of the infant brain (ages 2-35 months) in native space to language and speech and their association with structural asymmetries both in anatomical regions (sROIs) and subject-specific functional regions (fROIs).
Methods:
All infants completed at least one high-resolution T1-weighted MPRAGE scan (TR=2300ms, TE=2.9ms, voxel size=1.00 isotropic). We repeated structural scans until data quality was high enough for subsequent processing based on visual inspection during data acquisition. Structural data was processed using FreeSurfer's infant_recon_all (Zollei, 2020), visually checked for correctness. The outputs were used to examine height/depth of brain folds and curvature. Additionally, each infant completed at least two runs of a language localizer task (all TR=1000ms, TE=28ms, vox size=2x2x3mm) where they listened to audio recordings of male and female experimenters reading a children's book, with 3 conditions commonly used in language fMRI studies in adults: sentences (Sn), reverse sentences (Rv, Sn played in reverse; controls length, prosody and tone, but speech is meaningless) , and a texturized sound condition (Tx, auditorily degraded Sn, unrecognizable as speech, low-level auditory control). All functional data was preprocessed with a similar protocol and exclusion criteria as prior fMRI work in infants (Deen 2017, Kosakowski, 2022). Functional to anatomical registration was completed using FSL's linear registration tool, FLIRT (Jenkinson 2001 & 2002) (affine, 12 dof; best registration method across all infants), and all registrations were visually examined for accuracy. Resulting GLM contrast were applied to an individualized-subject approach, mirroring rigor applied to adult neuroimaging, for creating fROIs (top 5% most responsive voxels in search spaces (Fedorenko, 2010); language Sn>Rv; speech SnRv>Tx). Anatomical parcellations in native space generated sROIs.
Results:
We found no evidence of language (Sn-Rv) or speech (SnRv-Tx) selectivity in the sROIs (except RH orbital inferior frontal), perhaps due to functional heterogeneity within anatomical regions. Additionally, we do not see clear anatomical asymmetries. However, when using fROIs we found evidence of speech selectivity in RH superior temporal and LH inferior frontal fROIs, and quite surprisingly some initial sensitivity to linguistic stimuli as compared to reverse speech in the LH inferior frontal fROI (Fig. 1B). Interestingly, we also see greater LH inferior frontal fROI sulcal depth than RH (Fig. 1C).
·Figure 1
Conclusions:
These results highlight the importance of individually-defining fROIs even in infants, and show novel evidence in support of the early emergence (and developmental timecourse) of language selectivity and laterality in frontal cortex. We also identify a possible anatomical substrate for the development of this uniquely human skill. Future investigations will explore longitudinal development of this structure-function relationship, connectivity asymmetries, and extended language network (e.g. cerebellum, Fig.1A).
Language:
Language Acquisition
Speech Perception
Lifespan Development:
Normal Brain Development: Fetus to Adolescence 1
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI) 2
Keywords:
Development
FUNCTIONAL MRI
Language
STRUCTURAL MRI
1|2Indicates the priority used for review
Provide references using author date format
Deen, B. (2017). Organization of high-level visual cortex in human infants. Nature communications, 8(1), 13995.
Dehaene-Lambertz, G. (2006). Nature and nurture in language acquisition: anatomical and functional brain-imaging studies in infants. Trends in neurosciences, 29(7), 367-373.
Fedorenko, E. (2010). New method for fMRI investigations of language: defining ROIs functionally in individual subjects. Journal of neurophysiology, 104(2), 1177-1194.
Kosakowski, H. L. (2022). Selective responses to faces, scenes, and bodies in the ventral visual pathway of infants. Current Biology, 32(2), 265-274.
M. Jenkinson. (2001). A global optimisation method for robust affine registration of brain images. Medical Image Analysis, 5(2):143-156
M. Jenkinson. (2002). Improved optimisation for the robust and accurate linear registration and motion correction of brain images. NeuroImage, 17(2):825-841.
Zöllei, L. (2020). Infant FreeSurfer: An automated segmentation and surface extraction pipeline for T1-weighted neuroimaging data of infants 0–2 years. Neuroimage, 218, 116946.