Neural Correlates of the Development of Word Laterality in the Visual Word Form Area (VWFA) During Early Childhood

Abstract

Introduction: Humans have long been fascinated with how the brain is organized to support complex cognitive functions. One key finding is cortical specialization; the brain harbors many regions specialized to carry out specific cognitive functions. Many of these functional regions display lateralization, meaning they are more specialized to one hemisphere than the other. The Visual Word Form Area (VWFA) is one such region. The VWFA is an area of ventral temporal cortex (VTC) specialized for written scripts, and it develops category selectivity only after literacy. In adults, this word selectivity is dominant on the left. The experience dependent nature of the VWFA makes it a prime opportunity to investigate the development of functional laterality in the human brain, potentially revealing domain general mechanisms also related to the development of other lateralized functions. Therefore, we ask, what neural correlates relate to the development of word laterality in young children? Methods: We tested two potential sources of this word laterality: 1) structural connectivity of the VWFA with the high-level language network in frontal and temporal cortices and 2) activation in these language regions. To do so, we scanned reading children (4-13 years) on a visual fMRI task to define word and face regions as well as a separate auditory fMRI localizer to estimate language responses and collected diffusion-weighted imaging (DWI) to examine white matter connectivity. We defined face, word, and (spoken) language regions for each individual child and independent runs were used to extract activation to each condition to calculate selectivity and laterality; probabilistic tractography was used to quantify white matter connections between these regions. Results: Word selectivity was significantly left lateralized in our sample of young children. The magnitude of word laterality did not correlate with age, indicating variability in word laterality may be driven by other factors. Word laterality was positively and significantly related to laterality of the VWFA’s connectivity with frontal language regions. Additionally, word laterality correlated with auditory language selectivity in both frontal and temporal language regions. Laterality of language selectivity in these same regions was also positively and significantly related to word laterality. Conclusion: Our findings suggest that both connectivity to related regions and activation patterns in those connected regions may play a role in the development of functional laterality. Additionally, our investigations shed further light on the development of the neural circuitry that underlies reading behavior.OSU Center for Cognitive and Behavioral Brain Imaging (CCBBI), 2024 Gibson Research AwardThe College of Arts & Sciences at OSU (Dr. Saygin)The Chronic Brain Injury program at OSU (Dr. Saygin)R01 HD110401-01 (Dr. Saygin)A one-year embargo was granted for this item.Academic Major: Neuroscienc