Progressive development of reading comprehension fluency from late childhood to early adolescence is remarkably linked to changes in the temporal dynamics of visual word recognition. EEG/ERP based measures of how an individual participant's cortical timing for visual word recognition change over development are limited by low reliability. We present a novel approach to this challenge that individually models cortical latency to visual word forms by extracting phase values from Steady-State Visual Evoked Potentials (SSVEPs) for each participant. The resulting precise and reliable timing information for neural signatures underlying visual word form processes help account for the development of fluent reading comprehension. Typically developing readers (n=68), aged 8-15 years, viewed streams of four-character stimuli presented at 3 Hz, which evoked large significant power spikes from every participant. Linear phase by frequency functions across harmonics at 3, 6, and 9 Hz were consistent with a delay model, indicating a mean latency of 170 ms. Subject-level latencies revealed (a) high internal consistency (r=.94); (b) stability across variations in character-level (letters, unfamiliar pseudo-characters) and word-form level (words, nonwords, pseudofont strings) manipulations; (c) a linear relationship with age; and most remarkably, (d) a strong relationship with individual variation in the fluency of reading comprehension, that was (e) mediated by word naming speed. Results suggest a promising new approach for investigating the neural basis of reading development across several levels of processes, with temporal precision at the individual level that holds translational significance for promoting population-level fluency in reading comprehension.

The development of fluent literacy skills from childhood to adolescence is strongly constrained by the temporal dynamics of word recognition. Capturing the neural basis of these subtle timing changes in word recognition has remained challenging with EEG measures that lack reliability at the individual subject level. Here, we leverage phase information from Steady-State Visual Evoked Potentials (SSVEPs) to derive precise and reliable temporal dynamics of neural signatures underlying visual word form recognition at the individual level and examine their relationship to reading fluency and comprehension. Typically developing readers (N = 68), aged 8-15 years, viewed a stream of four-character stimulus strings presented at 3 Hz. Significant SSVEP signals emerged for nearly all participants. Signals at 3, 6, and 9 Hz harmonics exhibited a phase pattern consistent with a delay model, indicating a mean latency of approximately 170 milliseconds. Individual variations in latencies demonstrated (a) high internal consistency (R = .94); (b) stability across variations in letter string forms (familiar words, nonwords with familiar letters, nonwords with unfamiliar pseudo-characters); (c) a linear relationship with age; and most remarkably, (d) a predictive relationship with individual variation in reading fluency and reading comprehension. These results establish SSVEP visual word form latency as a promising approach for investigating the neural basis of reading development, paving the way for future translational applications in education and offering potential solutions to broader societal challenges in promoting population-level reading fluency. ### Competing Interest Statement The authors have declared no competing interest.

Early readers encounter thousands of printed words in children’s books. The frequency with which they see each word shapes both neural and behavioral responses. Teachers also introduce novel written words through short, intensive learning experiences. Here we combined steady-state visual evoked potentials (SSVEP), corpus-based word frequency counts, and a novel two-week classroom “learning sprint” to examine and compare these two forms of experience-dependent plasticity. Cortical responses at 4 Hz to contrasts between real words of varying frequency (high: on average 1000 per million; medium: on average 200 per million) and pseudowords were sensitive to corpus-based frequency estimates—marking the first such finding using SSVEP. Strikingly, newly acquired low-frequency words (<1 per million)—taught in a child’s own classroom versus counterbalanced words taught in two other classrooms—elicited cortical responses nearly identical to those evoked by high-frequency words versus pseudowords. Furthermore, 1 Hz responses to new vocabulary learning was linked to individual differences in reading skills, including word decoding and rapid automatic naming. Together, these findings highlight the causal impact of authentic instruction and the value of neuroscience-informed methods in education research.

This study aims to investigate the impact of vocabulary acquisition through short-term classroom learning and its relation to broader forms of vocabulary learning through long-term exposure in daily life. Through a two week of “learning sprint” in collaboration with a local elementary school and EEG-Steady State Visual Evoked Potentials (EEG-SSVEP) paradigm, we assessed new vocabulary learning in first and second graders within their pedagogical environment. We then compared the results with the word frequency effect, a well-established phenonmenon that reflects long-term vocabulary learning. After two weeks of classroom instruction, newly acquired words elicited neural responses similar to those of high-frequency words, with the effect significantly correlated with children’s phonological decoding skills. Additionally, we successfully replicated the word frequency effect using the SSVEP paradigm for the first time. These findings highlight the potential of the “learning sprint” model for conducting neuroscience research in authentic educational settings, thereby fostering a stronger connection between education and neuroscience. ### Competing Interest Statement The authors have declared no competing interest.

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 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 Highlights Longitudinal changes in cognitive responses to coarse print tuning, visual word from structure, and whole word representation were examined in early readers. Visual word form structure processing demonstrated striking patterns of growth with nearly doubled in EEG amplitude and increased left lateralization. Longitudinal changes in brain responses to visual word form structural information were linked to the growth in rapid automatic naming for letters. No longitudinal changes were observed for whole word representation processing and coarse tuning for print.

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. maximally significant relations were found between response amplitudes to words-pseudowords contrast and 145 pseudowords–nonwords contrast.

There are multiple levels of processing relevant to reading that vary in their visual, sublexical, and lexical orthographic processing demands. Segregating distinct cortical sources for each of these levels has been challenging in EEG studies of early readers. To address this challenge, we applied recent advances in analyzing high-density EEG using Steady-State Visual Evoked Potentials (SSVEPs) via data-driven Reliable Components Analysis (RCA) in a group of early readers spanning from kindergarten to second grade. Three controlled stimulus contrasts-familiar words versus unfamiliar pseudofonts, familiar words versus pseudowords, and pseudowords versus nonwords-were used to isolate coarse print tuning, lexical processing, and sublexical orthography-related processing, respectively. First, three overlapping yet distinct neural sources-left vOT, dorsal parietal, and primary visual cortex were revealed underlying coarse print tuning. Second, we segregated distinct cortical sources for the other two levels of processing: lexical fine tuning over occipito-temporal/parietal regions; sublexical orthographic fine tuning over left occipital regions. Finally, exploratory group analyses based on children's reading fluency suggested that coarse print tuning emerges early even in children with limited reading knowledge, while sublexical and higher-level lexical processing emerge only in children with sufficient reading knowledge. RESEARCH HIGHLIGHTS: Cognitive processes underlying coarse print tuning, sublexical, and lexical fine tuning were examined in beginning readers. Three overlapping yet distinct neural sources-left ventral occipito-temporal (vOT), left temporo-parietal, and primary visual cortex-were revealed underlying coarse print tuning. Responses to sublexical orthographic fine tuning were found over left occipital regions, while responses to higher-level linguistic fine tuning were found over occipito-temporal/parietal regions. Exploratory group analyses suggested that coarse print tuning emerges in children with limited reading knowledge, while sublexical and higher-level linguistic fine tuning effects emerge in children with sufficient reading knowledge.

EEG has been central to investigations of the time course of various neural functions underpinning visual word recognition. Recently the steady-state visual evoked potential (SSVEP) paradigm has been increasingly adopted for word recognition studies due to its high signal-to-noise ratio. Such studies, however, have been typically framed around a single source in the left ventral occipitotemporal cortex (vOT). Here, we combine SSVEP recorded from 16 adult native English speakers with a data-driven spatial filtering approach-Reliable Components Analysis (RCA)-to elucidate distinct functional sources with overlapping yet separable time courses and topographies that emerge when contrasting words with pseudofont visual controls. The first component topography was maximal over left vOT regions with a shorter latency (approximately 180 ms). A second component was maximal over more dorsal parietal regions with a longer latency (approximately 260 ms). Both components consistently emerged across a range of parameter manipulations including changes in the spatial overlap between successive stimuli, and changes in both base and deviation frequency. We then contrasted word-in-nonword and word-in-pseudoword to test the hierarchical processing mechanisms underlying visual word recognition. Results suggest that these hierarchical contrasts fail to evoke a unitary component that might be reasonably associated with lexical access.

There are multiple levels of processing relevant to reading that vary in their visual, sublexical and lexical orthographic processing demands. Segregating distinct cortical sources for each of these levels has been challenging in EEG studies of early readers. To address this challenge, we applied recent advances in analyzing high-density EEG using Steady-State Visual Evoked Potentials (SSVEPs) via data-driven Reliable Components Analysis (RCA) in a group of early readers spanning from kindergarten to second grade. Three controlled stimulus contrasts—familiar words versus unfamiliar pseudofonts, familiar words versus orthographically legal pseudowords, and orthographically legal pseudowords versus orthographically illegal nonwords—were used to isolate visual print/letter selectivity, sublexical processing, and lexical processing, respectively. We found robust responses specific to each of these processing levels, even in kindergarteners who have limited knowledge of print. Moreover, comparing amplitudes of these three stimulus contrasts across three reading fluency-based groups and three grade-based groups revealed fluency group and grade group main effects only for lexical contrast (i.e., words versus orthographically legal pseudowords). Furthermore, we found that sublexical orthography-related responses shifted their topographic distribution from the right to left hemisphere from kindergarten to first and second grades. Results suggest that, with more sensitive measures, the sublexical and lexical fine tuning for words—as a bio-marker of reading ability—can be detected at a much earlier stage than previously assumed. Declarations of interest None

Learning print-speech sound correspondences is a crucial step at the beginning of reading acquisition and often impaired in children with developmental dyslexia. Despite increasing insight into audiovisual language processing, it remains largely unclear how integration of print and speech develops at the neural level during initial learning in the first years of schooling. To investigate this development, 32 healthy, German-speaking children at varying risk for developmental dyslexia (17 typical readers and 15 poor readers) participated in a longitudinal study including behavioral and fMRI measurements in first (T1) and second (T2) grade. We used an implicit audiovisual (AV) non-word target detection task aimed at characterizing differential activation to congruent (AVc) and incongruent (AVi) audiovisual non-word pairs. While children's brain activation did not differ between AVc and AVi pairs in first grade, an incongruency effect (AVi > AVc) emerged in bilateral inferior temporal and superior frontal gyri in second grade. Of note, pseudoword reading performance improvements with time were associated with the development of the congruency effect (AVc > AVi) in the left posterior superior temporal gyrus (STG) from first to second grade. Finally, functional connectivity analyses indicated divergent development and reading expertise dependent coupling from the left occipito-temporal and superior temporal cortex to regions of the default mode (precuneus) and fronto-temporal language networks. Our results suggest that audiovisual integration areas as well as their functional coupling to other language areas and areas of the default mode network show a different development in poor vs. typical readers at varying familial risk for dyslexia.

How and when top-down information modulates visual-orthographic processing is an essential question in reading research. In a previous study, we showed that task modulation of print-tuning started at around 170 ms after stimulus presentation in the N1 offset of the ERP, while the N1 onset was yet unaffected. Here we test how prior category-level expectation affects visual-orthographic processing. Familiar, left/right-structured Chinese characters and stroke number matched, unfamiliar Korean characters were presented, while expectation about the upcoming stimuli was manipulated with green and blue colored frames (high Chinese vs. high Korean expectation). EEG data of 18 native Chinese speakers were recorded while participants performed an expectation judgment task. Results from occipito-temporal and whole map analyses revealed that effects of prior expectation changed throughout the N1. Accordingly in the N1 onset, a print tuning main effect was found, with a stronger N1 to Chinese characters than Korean characters, irrespective of expectation. In the N1 offset, an expectation-by-character interaction was observed at the whole map level, with a more negative N1 to Korean characters than Chinese characters when expecting a Chinese character, but no such difference when expecting a Korean character. Moreover, the expectation-by-character interaction continued to the N250, with similar responses to Chinese and Korean characters under the Chinese expectation condition, while less negative N250 to Korean than Chinese under the Korean expectation condition. Taken together, the current study provides evidence that prior category-level expectation starts to take effect at an early stage even within 200 ms by facilitating the processing of expected stimuli, suggesting that category-level expectation can influence early visual-orthographic processing during word recognition.

Fast neural tuning to print has been found within the first 250 ms of stimulus processing across different writing systems, indicated by larger N1 negativity in the ERP to words (or characters) compared to-control stimuli, such as symbols. However, whether print tuning effects can be modulated by task demands at early stages of visual word recognition is still under debate. To further explore this issue, an ERP study in Chinese was conducted. Familiar, high-frequency, left/right-structured Chinese characters and unfamiliar, stroke number-matched symbols (Korean characters) were used as stimulus conditions. While viewing the characters and symbols, 20 native Chinese speakers performed three tasks: delayed naming, repetition detection, and blue color detection. Results from occipito-temporal and whole map analyses suggest that the influence of task on print tuning changes throughout the N1. Accordingly in the N1 onset, a print tuning main effect was found, with a stronger N1 to words than symbols, irrespective of task. In the N1 offset, a print-by-task interaction reflected a more negative N1 to symbols than words in both delayed naming and color detection, but not in the repetition detection. After the N1 an N2 was observed with task and condition main effects at the whole map level. Taken together, the current study provides evidence that neural tuning to print is modulated by task demands already within the first 250 ms, suggesting that early visual-orthographic processing may be less automatic than it was thought, and the possible top-down modulation may be much faster than it was previously assumed.

A number of studies have explored the time course of Chinese semantic and syntactic processing. However, whether syntactic processing occurs earlier than semantics during Chinese sentence reading is still under debate. To further explore this issue, an event-related potentials (ERPs) experiment was conducted on 21 native Chinese speakers who read individually-presented Chinese simple sentences (NP1+VP+NP2) word-by-word for comprehension and made semantic plausibility judgments. The transitivity of the verbs was manipulated to form three types of stimuli: congruent sentences (CON), sentences with a semantically violated NP2 following a transitive verb (semantic violation, SEM), and sentences with a semantically violated NP2 following an intransitive verb (combined semantic and syntactic violation, SEM+SYN). The ERPs evoked from the target NP2 were analyzed by using the Residue Iteration Decomposition (RIDE) method to reconstruct the ERP waveform blurred by trial-to-trial variability, as well as by using the conventional ERP method based on stimulus-locked averaging. The conventional ERP analysis showed that, compared with the critical words in CON, those in SEM and SEM+SYN elicited an N400-P600 biphasic pattern. The N400 effects in both violation conditions were of similar size and distribution, but the P600 in SEM+SYN was bigger than that in SEM. Compared with the conventional ERP analysis, RIDE analysis revealed a larger N400 effect and an earlier P600 effect (in the time window of 500-800 ms instead of 570-810ms). Overall, the combination of conventional ERP analysis and the RIDE method for compensating for trial-to-trial variability confirmed the non-significant difference between SEM and SEM+SYN in the earlier N400 time window. Converging with previous findings on other Chinese structures, the current study provides further precise evidence that syntactic processing in Chinese does not occur earlier than semantic processing.