Progress in elementary school reading linked to growth of cortical responses to familiar letter combinations within visual word forms

Abstract

Learning to read depends on the ability to extract precise details of letter combinations, which convey critical information that distinguishes tens of thousands of visual word forms. To support fluent reading skill, one crucial neural developmental process is one's ability to rewire visual cortical circuitry to take advantage of statistical constraints inherent in combining letters into visual word forms. To test this idea in early readers, we tracked the impact of two years of schooling on within-student longitudinal changes in cortical responses to visual word forms and their growth in reading fluency. Three stimulus contrasts---words versus pseudofonts, words versus pseudowords, pseudowords versus nonwords---were presented while high-density EEG Steady-State Visual Evoked Potentials (SSVEPs, n=31) were recorded. Internalization of abstract visual word form structures over two years of reading experience resulted in a near doubling of SSVEP amplitude, with increasing left lateralization. Cortical entrainment by such word form structural information predicted the growth in reading fluency. However, no such changes were observed for whole word representation processing. Collectively, these findings indicate that sensitivity to visual word form structure develops rapidly through exposure to print and is uniquely linked to growth in reading fluency.