N1 and P2 to words and wordlike stimuli in late elementary school children and adults

Differences in the Efficiency of Cognitive Control across Young Adulthood: An ERP Perspective

Young adulthood is a period of major life changes when everyday life becomes much more complex compared to adolescence. Such changes require highly efficient cognitive control. Developmental studies show that structural changes in the brain areas that support complex behavior continue into the early 20s. However, despite the fact that at the beginning of young adulthood, important behavioral and brain restructuring still occurs, most studies use broad age ranges for young adults (from 18 to 40 years of age) as a reference point for "adult" behavior. The aim of this study was to investigate age-related differences in the efficiency of cognitive control across young adulthood. In total, 107 individuals participated in this study and were divided into three age groups: 19-21, 23-26, and 28-44. We used a visual word categorization task to assess cognitive efficiency and event-related potentials (ERPs) to track events that take place from the stimulus onset until the actual behavioral response. We found age differences in both performance and amplitudes of the ERP components during the early stages of processing - P2 and N2. Our findings provide important evidence for the continuation of age-related changes in brain dynamics that underlie the efficiency of cognitive control even in the early 20s.

The odd one out - Orthographic oddball processing in children with poor versus typical reading skills in a fast periodic visual stimulation EEG paradigm

The specialization of left ventral occipitotemporal brain regions to automatically process word forms develops with reading acquisition and is diminished in children with poor reading skills (PR). Using a fast periodic visual oddball stimulation (FPVS) design during electroencephalography (EEG), we examined the level of sensitivity and familiarity to word form processing in ninety-two children in 2nd and 3rd grade with varying reading skills (n = 35 for PR, n = 40 for typical reading skills; TR). To test children's level of "sensitivity", false font (FF) and consonant string (CS) oddballs were embedded in base presentations of word (W) stimuli. "Familiarity" was examined by presenting letter string oddballs with increasing familiarity (CS, pseudoword - PW, W) in FF base stimuli. Overall, our results revealed stronger left-hemispheric coarse sensitivity effects ("FF in W" > "CS in W") in TR than in PR in both topographic and oddball frequency analyses. Further, children distinguished between orthographically legal and illegal ("W/PW in FF" > "CS in FF") but not yet between lexical and non-lexical ("W in FF" vs "PW in FF") word forms. Although both TR and PR exhibit visual sensitivity and can distinguish between orthographically legal and illegal letter strings, they still struggle with nuanced lexical distinctions. Moreover, the strength of sensitivity is linked to reading proficiency. Our work adds to established knowledge in the field to characterize the relationship between print tuning and reading skills and suggests differences in the developmental progress to automatically process word forms.

Neural specialization to English words in Chinese children: Joint contribution of age and English reading abilities

N1 tuning to words, a neural marker of visual word recognition, develops by an interaction between age and ability. The development of N1 tuning to a second learnt print is unclear. The present study examined the joint contribution of age and English reading abilities to N1 amplitude and tuning to English print in Chinese children in Hong Kong. EEG signals were recorded from 179 children (six to nine years old) while they were performing a repetition detection task comprised of different print stimuli measuring three types of tuning, i.e., coarse tuning (real word versus false font), fine tuning (real versus nonword), and lexicality effect (real versus pseudo word). Children were assessed in English word reading accuracy (EWR) and English sub-lexical orthographic knowledge (EOK). Results indicated that coarse tuning decreased with age but increased with EWR and EOK. Fine tuning uniquely increased with EOK, and the lexicality effect increased with EWR. At last, higher EWR was linked to less right-lateralized coarse tuning in younger children. Taken together, the findings support the visual perceptual expertise account in the L2 context, in that N1 coarse tuning, fine tuning, and lexicality effect are driven by skill improvement.

Event-related potential and lexical decision task in dyslexic adults: Lexical and lateralization effects

Developmental dyslexia is a specific learning disorder that presents cognitive and neurobiological impairments related to different patterns of brain activation throughout development, continuing in adulthood. Lexical decision tasks, together with electroencephalography (EEG) measures that have great temporal precision, allow the capture of cognitive processes during the task, and can assist in the understanding of altered brain activation processes in adult dyslexics. High-density EEG allows the use of temporal analyses through event-related potentials (ERPs). The aim of this study was to compare and measure the pattern of ERPs in adults with developmental dyslexia and good readers, and to characterize and compare reading patterns between groups. Twenty university adults diagnosed with developmental dyslexia and 23 healthy adult readers paired with dyslexics participated in the study. The groups were assessed in tests of intelligence, phonological awareness, reading, and writing, as well as through the lexical decision test (LDT). During LDT, ERPs were recorded using a 128-channel EEG device. The ERPs P100 occipital, N170 occipito-temporal, N400 centro-parietal, and LPC centro-parietal were analyzed. The results showed a different cognitive profile between the groups in the reading, phonological awareness, and writing tests but not in the intelligence test. In addition, the brain activation pattern of the ERPs was different between the groups in terms of hemispheric lateralization, with higher amplitude of N170 in the dyslexia group in the right hemisphere and opposite pattern in the control group and specificities in relation to the items of the LDT, as the N400 were more negative in the Dyslexia group for words, while in the control group, this ERP was more pronounced in the pseudowords. These results are important for understanding different brain patterns in developmental dyslexia and can better guide future interventions according to the changes found in the profile.

Behavioral and electrophysiological analyses of written word processing in spoken and literary Arabic: New insights into the diglossia question

Diglossia in Arabic describes the existence and the use of two varieties of the same language: spoken Arabic (SA) and literary Arabic (LA). SA, the dialect first spoken by Arabic native speakers, is used in non‐formal situations for everyday conversations, and varies from one region to another in the Arabic world. LA, acquired later in life when the children learn to read and write at school, is used for formal purposes such as media, speeches in public and religious sermons. Previous research showed that, in the auditory modality, SA words are processed faster than LA ones. In the visual modality, written LA words are processed faster than SA ones, the latter comparing with low‐frequency words. This study analysed event‐related potentials (ERPs) during the processing of high‐frequency (LAHF), LA low‐frequency (LALF) and SA high‐frequency words (SAHF) in a visual lexical decision task. Faster reaction times were observed for LAHF, followed by SAHF and then by LALF. ERPs showed a modulation of the early components starting from the P100 component and of the late P600 component, supposedly related to memory processes. These findings, indicating that processing written SAHF words was largely comparable with processing of LALF, are discussed in the context of Arabic diglossia.

Typical and Atypical Development of Visual Expertise for Print as Indexed by the Visual Word N1 (N170w): A Systematic Review

The visual word N1 (N170w) is an early brain ERP component that has been found to be a neurophysiological marker for print expertise, which is a prelexical requirement associated with reading development. To date, no other review has assimilated existing research on reading difficulties and atypical development of processes reflected in the N170w response. Hence, this systematic review synthesized results and evaluated neurophysiological and experimental procedures across different studies about visual print expertise in reading development. Literature databases were examined for relevant studies from 1995 to 2020 investigating the N170w response in individuals with or without reading disorders. To capture the development of the N170w related to reading, results were compared between three different age groups: pre-literate children, school-aged children, and young adults. The majority of available N170w studies (N = 69) investigated adults (n = 31) followed by children (school-aged: n = 21; pre-literate: n = 4) and adolescents (n = 1) while some studies investigated a combination of these age groups (n = 12). Most studies were conducted with German-speaking populations (n = 17), followed by English (n = 15) and Chinese (n = 14) speaking participants. The N170w was primarily investigated using a combination of words, pseudowords, and symbols (n = 20) and mostly used repetition-detection (n = 16) or lexical-decision tasks (n = 16). Different studies posed huge variability in selecting electrode sites for analysis; however, most focused on P7, P8, and O1 sites of the international 10–20 system. Most of the studies in adults have found a more negative N170w in controls than poor readers, whereas in children, the results have been mixed. In typical readers, N170w ranged from having a bilateral distribution to a left-hemispheric dominance throughout development, whereas in young, poor readers, the response was mainly right-lateralized and then remained in a bilateral distribution. Moreover, the N170w latency has varied according to age group, with adults having an earlier onset yet with shorter latency than school-aged and pre-literate children. This systematic review provides a comprehensive picture of the development of print expertise as indexed by the N170w across age groups and reading abilities and discusses theoretical and methodological differences and challenges in the field, aiming to guide future research.

Dynamic functional brain network connectivity during pseudoword processing relates to children's reading skill

Learning to read requires children to link print (orthography) with its corresponding speech sounds (phonology). Yet, most EEG studies of reading development focus on emerging functional specialization (e.g., developing increasingly refined orthographic representations), rather than directly measuring the functional connectivity that links orthography and phonology in real time. In this proof-of-concept study we relate children's reading skill to both orthographic specialization for print (via the N170, also called the N1, event related potential, ERP) and orthographic-phonological integration (via dynamic/event-related EEG phase synchronization - an index of functional brain network connectivity). Typically developing English speaking children (n = 24; 4-14 years) and control adults (n = 20; 18-35 years) viewed pseudowords, consonants and unfamiliar false fonts during a 1-back memory task while 64-channel EEG was recorded. Orthographic specialization (larger N170 for pseudowords vs. false fonts) became more left-lateralized with age, but not with reading skill. Conversely, children's reading skill correlated with functional brain network connectivity during pseudoword processing that requires orthography-phonology linking. This was seen during two periods of simultaneous low frequency synchronization/high frequency desynchronization of posterior-occipital brain network activity. Specifically, in stronger readers, left posterior-occipital activity showed more delta (1-3Hz) synchronization around 300-500 ms (simultaneous with gamma 30-80 Hz desynchronization) and more gamma desynchronization around 600-1000 ms (simultaneous with theta 3-7Hz synchronization) during pseudoword vs. false font processing. These effects were significant even when controlling for age (moderate - large effect sizes). Dynamic functional brain network connectivity measures the brain's real-time sound-print linking. It may offer an under-explored, yet sensitive, index of the neural plasticity associated with reading development.

The time course of processing handwritten words: An ERP investigation

Behavioral studies have shown that the legibility of handwritten script hinders visual word recognition. Furthermore, when compared with printed words, lexical effects (e.g., word-frequency effect) are magnified for less intelligible (difficult) handwriting (Barnhart and Goldinger, 2010; Perea et al., 2016). This boost has been interpreted in terms of greater influence of top-down mechanisms during visual word recognition. In the present experiment, we registered the participants' ERPs to uncover top-down processing effects on early perceptual encoding. Participants' behavioral and EEG responses were recorded to high- and low-frequency words that varied in script's legibility (printed, easy handwritten, difficult handwritten) in a lexical decision experiment. Behavioral results replicated previous findings: word-frequency effects were larger in difficult handwriting than in easy handwritten or printed conditions. Critically, the ERP data showed an early effect of word-frequency in the N170 that was restricted to the difficult-to-read handwritten condition. These results are interpreted in terms of increased attentional deployment when the bottom-up signal is weak (difficult handwritten stimuli). This attentional boost would enhance top-down effects (e.g., lexical effects) in the early stages of visual word processing.

Uncoupled Brain and Behavior Changes in Lexical, Phonological, and Memory Processing in Struggling Readers

Paired behavioral and ERP measures were used to track change over time in 17 third- and fourth-grade struggling readers. Word and nonword reading on standardized tests improved, but differentiation of words and letter strings, measured by N170 and N400 amplitude, did not significantly change. Sound awareness scores improved, but the ERP rhyming effect did not significantly change. Both digit span scores and latency of the P300 oddball effect decreased. Correlations between the ostensibly matched behavioral and electrophysiological measures of change were not significant, indicating that use of ERP and behavioral measures can provide nonoverlapping insight into change during reading development.

Developmental changes in neural letter-selectivity: A 1-year follow-up of beginning readers

The developmental course of neural tuning to visual letter strings is unclear. Here we tested 39 children longitudinally, at the beginning of grade 1 (6.45 ± 0.33 years old) and 1 year after, with fast periodic visual stimulation in electroencephalography to assess the evolution of selective neural responses to letter strings and their relationship with emerging reading abilities. At both grades, frequency-tagged letter strings were discriminated from pseudofont strings (i.e. letter-selectivity) over the left occipito-temporal cortex, with effects observed at the individual level in 62% of children. However, visual words were not discriminated from pseudowords (lexical access) at either grade. Following 1 year of schooling, letter-selective responses showed a specific increase in amplitude, a more complex pattern of harmonics, and were located more anteriorly over the left occipito-temporal cortex. Remarkably, at both grades, neural responses were highly significant at the individual level and correlated with individual reading scores. The amplitude increase in letter-selective responses between grades was not found for discrimination responses of familiar keyboard symbols from pseudosymbols, and was not related to a general increase in visual stimulation responses. These findings demonstrate a rapid onset of left hemispheric letter selectivity, with 1 year of reading instruction resulting in increased emerging reading abilities and a clear quantitative and qualitative evolution within left hemispheric neural circuits for reading.

Visual word form processing deficits driven by severity of reading impairments in children with developmental dyslexia

The visual word form area (VWFA) in the left ventral occipito-temporal (vOT) cortex is key to fluent reading in children and adults. Diminished VWFA activation during print processing tasks is a common finding in subjects with severe reading problems. Here, we report fMRI data from a multicentre study with 140 children in primary school (7.9-12.2 years; 55 children with dyslexia, 73 typical readers, 12 intermediate readers). All performed a semantic task on visually presented words and a matched control task on symbol strings. With this large group of children, including the entire spectrum from severely impaired to highly fluent readers, we aimed to clarify the association of reading fluency and left vOT activation during visual word processing. The results of this study confirm reduced word-sensitive activation within the left vOT in children with dyslexia. Interestingly, the association of reading skills and left vOT activation was especially strong and spatially extended in children with dyslexia. Thus, deficits in basic visual word form processing increase with the severity of reading disability but seem only weakly associated with fluency within the typical reading range suggesting a linear dependence of reading scores with VFWA activation only in the poorest readers.

Word processing deficits in children with isolated and combined reading and spelling deficits: An ERP-study

Dissociations between reading and spelling deficits are likely to be associated with distinct deficits in orthographic word processing. To specify differences in automatic visual word recognition, the current ERP-study compared children with isolated reading fluency deficits (iRD), isolated spelling deficits (iSD), and combined reading fluency and spelling deficits (cRSD) as well as typically developing (TD) 10-year-olds while performing a variant of the Reicher-Wheeler paradigm: children had to indicate which of two letters occurred at a given position in a previously presented word, legal pseudoword, illegal pseudoword or nonword. Event-related potentials (N200 and N400) associated with sublexical orthographic and lexical orthographic processing as well as phonological word processing were analyzed. All groups showed a word superiority effect, both on the behavioral and the neurophysiological level. Group differences occurred for phonological word processing. TD and iRD groups showed a higher N400 activation for illegal pseudowords than for nonwords, while the two spelling deficit groups showed no activation differences between these two stimuli conditions. The findings suggest that differences in phonological word processing are associated with spelling problems: children with iSD showed reduced sensitivity for phonological word processing, while these deficits were not evident in children with iRD.

Simultaneous EEG and fMRI reveals stronger sensitivity to orthographic strings in the left occipito-temporal cortex of typical versus poor beginning readers

The level of reading skills in children and adults is reflected in the strength of preferential neural activation to print. Such preferential activation appears in the N1 event-related potential (ERP) over the occipitotemporal scalp after around 150–250 ms and the corresponding blood oxygen level dependent (BOLD) signal in the ventral occipitotemporal (vOT) cortex. Here, orthography-sensitive (print vs. false font) processing was examined using simultaneous EEG-fMRI in 38 first grade children with poor and typical reading skills, and at varying familial risk for developmental dyslexia. Coarse orthographic sensitivity was observed as an increased activation to print in the N1 ERP and in the BOLD signal of individually varying vOT regions in 57% of beginning readers. Finer differentiation in processing orthographic strings (words vs. nonwords) further occurred in specific vOT clusters. Neither method alone showed robust differences in orthography-sensitive processing between typical and poor reading children. Importantly, using single-trial N1 ERP-informed fMRI analysis, we found differential modulation of the orthography-sensitive BOLD response in the left vOT for typical readers only. This result, thus, confirms subtle functional alterations in a brain structure known to be critical for fluent reading at the very beginning of reading instruction.

N1 lateralization and dyslexia: An event-related potential study in children with a familial risk of dyslexia

The rapid automatic specialized processing of printed words is signalled by the left-lateralization of the N1 component in the visual event-related potential (ERP). In the present study, we have investigated whether differences in N1 lateralization can be observed between Dutch children with and without (a familial risk of) dyslexia around the age of 12 years using a linguistic judgement task. Forty-five participants were included in the ERP analysis, 18 in the low familial risk group without dyslexia, 15 in the high familial risk group without dyslexia, and 12 in the high familial risk group with dyslexia. The results showed that although the N1 peaked slightly earlier in the left hemisphere, the N1 amplitude was right-lateralized in all groups. Moreover, there were no group differences in N1 amplitude or latency, and there was no relationship between reading (related) test scores and N1 characteristics. The results of the present study and our previous findings in adults suggest that print-tuning lateralization is a process that is still developing in adolescence. Because other studies did find N1 lateralization in younger readers with a print versus nonprint contrast, the current results seem to indicate that differences in N1 lateralization also depend on the experimental paradigm.

Early lexical processing of Chinese words indexed by Visual Mismatch Negativity effects

Although Mismatch Negativity (MMN) effects indicating early, automatic lexical processing have been reported in the auditory language modality, so far these have not been reliably obtained in MMN studies of visual word recognition. The present study explores this discrepancy by investigating whether visual MMN (vMMN) effects can be obtained in written Chinese single-character word recognition. While participants were engaged in a non-linguistic distraction task, we measured Event-Related Potentials (ERPs) time-locked to perifoveally-presented real and pseudo- characters matched in overall visual-orthographic attributes. VMMN was defined as significant difference between the ERPs to characters presented as deviants or as standards in a context of non-characters. For the native Chinese readers, af ter sub-lexical structural detection from 120-160 ms, only real characters elicited vMMN at the interval of 170-210 ms, suggesting that lexical information in Chinese words is processed early and automatically. In a later window of 340-380 ms, both real and pseudo- characters yielded vMMNs. In a control group of non-Chinese participants, no evidence of vMMN was found for either real or pseudo-characters. Taken together, these results suggest that long-term memory representations for real characters may enable their early processing even in unattended conditions.

The N170 ERP component differs in laterality, distribution, and association with continuous reading measures for deaf and hearing readers

The temporo-occipitally distributed N170 ERP component is hypothesized to reflect print-tuning in skilled readers. This study investigated whether skilled deaf and hearing readers (matched on reading ability, but not phonological awareness) exhibit similar N170 patterns, given their distinct experiences learning to read. Thirty-two deaf and 32 hearing adults viewed words and symbol strings in a familiarity judgment task. In the N170 epoch (120-240ms) hearing readers produced greater negativity for words than symbols at left hemisphere (LH) temporo-parietal and occipital sites, while deaf readers only showed this asymmetry at occipital sites. Linear mixed effects regression was used to examine the influence of continuous measures of reading, spelling, and phonological skills on the N170 (120-240ms). For deaf readers, better reading ability was associated with a larger N170 over the right hemisphere (RH), but for hearing readers better reading ability was associated with a smaller RH N170. Better spelling ability was related to larger occipital N170s in deaf readers, but this relationship was weak in hearing readers. Better phonological awareness was associated with smaller N170s in the LH for hearing readers, but this association was weaker and in the RH for deaf readers. The results support the phonological mapping hypothesis for a left-lateralized temporo-parietal N170 in hearing readers and indicate that skilled reading is characterized by distinct patterns of neural tuning to print in deaf and hearing adults.

Altered patterns of directed connectivity within the reading network of dyslexic children and their relation to reading dysfluency

Reading is a complex cognitive skill subserved by a distributed network of visual and language-related regions. Disruptions of connectivity within this network have been associated with developmental dyslexia but their relation to individual differences in the severity of reading problems remains unclear. Here we investigate whether dysfunctional connectivity scales with the level of reading dysfluency by examining EEG recordings during visual word and false font processing in 9-year-old typically reading children (TR) and two groups of dyslexic children: severely dysfluent (SDD) and moderately dysfluent (MDD) dyslexics. Results indicated weaker occipital to inferior-temporal connectivity for words in both dyslexic groups relative to TRs. Furthermore, SDDs exhibited stronger connectivity from left central to right inferior-temporal and occipital sites for words relative to TRs, and for false fonts relative to both MDDs and TRs. Importantly, reading fluency was positively related with forward and negatively with backward connectivity. Our results suggest disrupted visual processing of words in both dyslexic groups, together with a compensatory recruitment of right posterior brain regions especially in the SDDs during word and false font processing. Functional connectivity in the brain's reading network may thus depend on the level of reading dysfluency beyond group differences between dyslexic and typical readers.

An event-related potential study of the relationship between N170 lateralization and phonological awareness in developing readers

As reading development progresses, the visual processing of word forms becomes increasingly left-lateralized. This is visible, among other ways, as increased left-lateralization of the N170 ERP component. A primary explanation of this effect, the phonological mapping hypothesis, proposes that the left-lateralization of visual word form processing that accompanies reading development is the result of calling upon left hemisphere auditory language regions to perform the linking of orthography with phonology (phonological mapping). A key, but untested, prediction of the phonological mapping hypothesis is thus that individuals with greater phonological awareness should exhibit more left lateralized visual processing of word forms than individuals with poorer phonological awareness. We set out to test this hypothesis here. We accomplished this by collecting ERPs while children grades 5-6 viewed words, objects, and word/object ambiguous items (e.g., "SMILE" shaped like a smile - hereafter referred to as wobjects). Results revealed that, consistent with the phonological mapping hypothesis, individual phonological awareness (but not other measures of reading development) predicted left-lateralization of the N170 component elicited in response to words (but not item types that were not word-like).

Behavioral and neurophysiological evidence for increased cognitive flexibility in late childhood

Executive functions, like the capacity to control and organize thoughts and behavior, develop from childhood to young adulthood. Although task switching and working memory processes are known to undergo strong developmental changes from childhood to adulthood, it is currently unknown how task switching processes are modulated between childhood and adulthood given that working memory processes are central to task switching. The aim of the current study is therefore to examine this question using a combined cue- and memory-based task switching paradigm in children (N = 25) and young adults (N = 25) in combination with neurophysiological (EEG) methods. We obtained an unexpected paradoxical effect suggesting that memory-based task switching is better in late childhood than in young adulthood. No group differences were observed in cue-based task switching. The neurophysiological data suggest that this effect is not due to altered attentional selection (P1, N1) or processes related to the updating, organization, and implementation of the new task-set (P3). Instead, alterations were found in the resolution of task-set conflict and the selection of an appropriate response (N2) when a task has to be switched. Our observation contrasts findings showing that cognitive control mechanisms reach their optimal functioning in early adulthood.