Starting to see a pattern: Longitudinal SSVEP signals reveal how growth in children's cortical sensitivity to visual word form structure is uniquely linked to two-year growth in reading fluency
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 ones brain sensitivity to 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-subject longitudinal changes in cortical responses to different properties of words (coarse tuning for print, and fine tuning to visual word forms and whole word representations) and their growth in reading skill. 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. Longitudinal changes in brain responses to such word form structural information were linked to the growth in reading, especially in rapid automatic naming for letters. No such changes were observed for whole word representation processing and coarse tuning for print. Collectively, these findings indicate that sensitivity to visual word form structure develops rapidly through exposure to print and is linked to growth in reading skill. Research HighlightsO_LILongitudinal changes in cognitive responses to coarse print tuning, visual word from structure, and whole word representation were examined in early readers. C_LIO_LIVisual word form structure processing demonstrated striking patterns of growth with nearly doubled in EEG amplitude and increased left lateralization. C_LIO_LILongitudinal changes in brain responses to visual word form structural information were linked to the growth in rapid automatic naming for letters. C_LIO_LINo longitudinal changes were observed for whole word representation processing and coarse tuning for print. C_LI