Semantic processing in children and adults: incongruity and the N400

Electrophysiological markers of orthographic pattern learning in school-aged children with reading challenges: An ERP investigation

BACKGROUND

Previous studies suggested that children with reading difficulty have impaired statistical learning ability in extracting distributional orthographic regularities. However, the neural mechanisms underlying have not been fully investigated.

AIMS

The current study aimed to identify the electrophysiological markers and to examine the neural underpinnings of statistical learning of orthographic regularities in children with reading difficulties.

METHODS AND PROCEDURES

Using the event-related potentials (ERPs) and the orthographic learning task, 157 children were exposed to a sequence of artificial pseudocharacters with varying levels of positional and semantic consistency (low at 60 %, moderate at 80 %, and high at 100 %).

OUTCOMES AND RESULTS

Poor readers elicited an increased N170 response in the low consistency and a lack of left-lateralized P300 effect when learning positional regularities of radicals. Similarly, larger N170 effects were observed in poor readers, while similar N400 effects were found in both poor and average readers when learning semantic regularities of radicals.

CONCLUSIONS AND IMPLICATIONS

Our findings indicate that poor readers may have trouble using statistical information for early-stage orthographic pattern extraction, yet they can identify semantic inconsistencies after sufficient exposure. These results deepen our understanding of the neural mechanisms involved in statistical learning for poor readers and aid in improving criteria for differentiating between typically developing children and those with reading challenges.

Understanding words in context: A naturalistic EEG study of children's lexical processing

When listening to speech, adults rely on context to anticipate upcoming words. Evidence for this comes from studies demonstrating that the N400, an event-related potential (ERP) that indexes ease of lexical-semantic processing, is influenced by the predictability of a word in context. We know far less about the role of context in children's speech comprehension. The present study explored lexical processing in adults and 5-10-year-old children as they listened to a story. ERPs time-locked to the onset of every word were recorded. Each content word was coded for frequency, semantic association, and predictability. In both children and adults, N400s reflect word predictability, even when controlling for frequency and semantic association. These findings suggest that both adults and children use top-down constraints from context to anticipate upcoming words when listening to stories.

Event-related Potential Measures of Visual Word Processing in Monolingual and Bilingual Children and Adults: A Focus on Word Frequency Effects

How does language background influence the neural correlates of visual word recognition in children? To address this question, we used an ERP lexical decision task to examine first-language (L1) and second-language (L2) visual word processing in monolingual and bilingual school-aged children and young adults (n = 123). In particular, we focused on the effects of word frequency (an index of lexical accessibility) on RTs and the N400 ERP component. Behaviorally, we found larger L1 versus L2 word frequency effects among bilingual children, driven by faster and more accurate responses to higher-frequency words (no other language or age group differences were observed). Neurophysiologically, we found larger L1 word frequency effects in bilinguals versus monolinguals (across both age groups), reflected in more negative ERP amplitudes to lower-frequency words. However, the bilingual groups processed L1 and L2 words similarly, despite lower levels of subjective and objective L2 proficiency. Taken together, our findings suggest that divided L1 experience (but not L2 experience) influences the neural correlates of visual word recognition across childhood and adulthood.

The interplay of semantic and syntactic processing across hemispheres

The current study investigated the hemispheric dynamics underlying semantic and syntactic priming in lexical decision tasks. Utilizing primed-lateralized paradigms, we observed a distinct pattern of semantic priming contingent on the priming hemisphere. The right hemisphere (RH) exhibited robust semantic priming irrespective of syntactic congruency between prime and target, underscoring its proclivity for semantic processing. Conversely, the left hemisphere (LH) demonstrated slower response times for semantically congruent yet syntactically incongruent word pairs, highlighting its syntactic processing specialization. Additionally, nonword data revealed a hemispheric divergence in syntactic processing, with the LH showing significant intrahemispheric syntactic priming. These findings illuminate the intrinsic hemispheric specializations for semantic and syntactic processing, offering empirical support for serial processing models. The study advances our understanding of the complex interplay between semantic and syntactic factors in hemispheric interactions.

It takes a village: A multi-brain approach to studying multigenerational family communication

Grandparents play a critical role in child rearing across the globe. Yet, there is a shortage of neurobiological research examining the relationship between grandparents and their grandchildren. We employ multi-brain neurocomputational models to simulate how changes in neurophysiological processes in both development and healthy aging affect multigenerational inter-brain coupling - a neural marker that has been linked to a range of socio-emotional and cognitive outcomes. The simulations suggest that grandparent-child interactions may be paired with higher inter-brain coupling than parent-child interactions, raising the possibility that the former may be more advantageous under certain conditions. Critically, this enhancement of inter-brain coupling for grandparent-child interactions is more pronounced in tri-generational interactions that also include a parent, which may speak to findings that grandparent involvement in childrearing is most beneficial if the parent is also an active household member. Together, these findings underscore that a better understanding of the neurobiological basis of cross-generational interactions is vital, and that such knowledge can be helpful in guiding interventions that consider the whole family. We advocate for a community neuroscience approach in developmental social neuroscience to capture the diversity of child-caregiver relationships in real-world settings.

Age-related differences in expectation-based novel word learning

Adult language users can infer the meaning of a previously unfamiliar word from a single exposure to this word in a semantically and thematically constrained context, henceforth, predictive context (Borovsky et al., 2010 Cognition, 116(2), 289-296; Borovsky et al., 2012 Language Learning and Development, 8(3), 278-302). Children use predictive contexts to anticipate upcoming stimuli (Borovsky et al., 2012 Language Learning and Development, 8(3), 278-302; Mani & Huettig, 2012 Journal of Experimental Psychology: Human Perception and Performance, 38(4), 843-847), but the extent to which they rely on prediction to learn novel word forms is unclear (Gambi et al., 2021 Cognition, 211, 104650). Here, we examine children's one-shot learning from predictive contexts using a modified version of the one-shot learning ERP paradigm for children aged 7-13 years. In a first learning phase, we presented audio recordings of expected words and unexpected novel pseudowords in strongly and weakly constraining sentence contexts. In the following priming phase, the same recorded words and pseudowords were used as primes to identical/synonymous, related, and unrelated target words. We measured N400 modulations to the word and pseudoword continuations in the learning phase and to the identical/synonymous, related, or unrelated target words in the priming phase. When initially presented in strongly constraining sentences, novel pseudowords primed synonymous targets equally well as word primes of the same intended meaning. This pattern was particularly pronounced in older children. Our findings suggest that, around early adolescence, children can use single exposures to constraining contexts to infer the meaning of novel words and to integrate these novel words in their lexicons.

The N400 ERP component reflects an error-based implicit learning signal during language comprehension

The functional significance of the N400 evoked-response component is still actively debated. An increasing amount of theoretical and computational modelling work is built on the interpretation of the N400 as a prediction error. In neural network modelling work, it was proposed that the N400 component can be interpreted as the change in a probabilistic representation of meaning that drives the continuous adaptation of an internal model of the statistics of the environment. These results imply that increased N400 amplitudes should correspond to greater adaptation, which can be measured via implicit memory. To investigate this model derived hypothesis, the current study manipulated expectancy in a sentence reading task to influence N400 amplitudes and subsequently presented the previously expected vs. unexpected words in a perceptual identification task to measure implicit memory. As predicted, reaction times in the perceptual identification task were significantly faster for previously unexpected words that induced larger N400 amplitudes in the previous sentence reading task. Additionally, it could be demonstrated that this adaptation seems to specifically depend on the process underlying N400 amplitudes, as participants with larger N400 differences during sentence reading also exhibited a larger implicit memory benefit in the perceptual identification task. These findings support the interpretation of the N400 as an implicit learning signal driving adaptation in language processing.

Implicit Semantic Processing of Linguistic and Non-linguistic Stimuli in Adults with Autism Spectrum Disorder

While many individuals with autism spectrum disorder (ASD) experience difficulties with language processing, non-linguistic semantic processing may be intact. We examined neural responses to an implicit semantic priming task by comparing N400 responses—an event-related potential related to semantic processing—in response to semantically related or unrelated pairs of words or pictures. Adults with ASD showed larger N400 responses than typically developing adults for pictures, but no group differences occurred for words. However, we also observed complex modulations of N400 amplitude by age and by level of autistic traits. These results offer important implications for how groups are delineated and compared in autism research.

The effects of background music on neural responses during reading comprehension

The effects of background speech or noise on visually based cognitive tasks has been widely investigated; however, little is known about how the brain works during such cognitive tasks when music, having a powerful function of evoking emotions, is used as the background sound. The present study used event-related potentials to examine the effects of background music on neural responses during reading comprehension and their modulation by musical arousal. Thirty-nine postgraduates judged the correctness of sentences about world knowledge without or with background music (high-arousal music and low-arousal music). The participants’ arousal levels were reported during the experiment. The results showed that the N400 effect, elicited by world knowledge violations versus correct controls, was significantly smaller for silence than those for high- and low-arousal music backgrounds, with no significant difference between the two musical backgrounds. This outcome might have occurred because the arousal levels of the participants were not affected by the high- and low-arousal music throughout the experiment. These findings suggest that background music affects neural responses during reading comprehension by increasing the difficulty of semantic integration, and thus extend the irrelevant sound effect to suggest that the neural processing of visually based cognitive tasks can also be affected by music.

Developmental differences in beta and theta power during sentence processing

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Changes in ERPs and oscillatory dynamic occur during auditory sentence processing.

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Adults are significantly better at identifying syntactic errors compared to children.

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Adults display a significant P600 effect and theta/beta power decrease.

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Children display a significant N400 effect and smaller decrease in theta/beta power.

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These findings suggest syntactic processing skills are still developing by age 12.

Although very young children process ongoing language quickly and effortlessly, research indicates that they continue to improve and mature in their language skills through adolescence. This prolonged development may be related to differing engagement of semantic and syntactic processes. This study used event related potentials and time frequency analysis of EEG to identify developmental differences in neural engagement as children (ages 10–12) and adults performed an auditory verb agreement grammaticality judgment task. Adults and children revealed very few differences in comprehending grammatically correct sentences. When identifying grammatical errors, however, adults displayed widely distributed beta and theta power decreases that were significantly less pronounced in children. Adults also demonstrated a significant P600 effect, while children exhibited an apparent N400 effect. Thus, when identifying subtle grammatical errors in real time, adults display greater neural activation that is traditionally associated with syntactic processing whereas children exhibit greater activity more commonly associated with semantic processing. These findings support previous claims that the cognitive and neural underpinnings of syntactic processing are still developing in adolescence, and add to them by more clearly identifying developmental changes in the neural oscillations underlying grammatical processing.

N400 Event-Related Potential and Standardized Measures of Reading in Late Elementary School Children: Correlated or Independent?

We investigated whether and how standardized behavioral measures of reading and electrophysiological measures of reading were related in 72 typically developing, late elementary school children. Behavioral measures included standardized tests of spelling, phonological processing, vocabulary, comprehension, naming speed, and memory. Electrophysiological measures were composed of the amplitude of the N400 component of the event-related potential waveform elicited by real words, pseudowords, nonpronounceable letter strings, and strings of letter-like symbols (false fonts). The only significant brain-behavior correlations were between standard scores on the vocabulary test and N400 mean amplitude to real words (r = -.272) and pseudowords (r = -.235). We conclude that, while these specific sets of standardized behavioral and electrophysiological measures both provide an index of reading, for the most part, they are independent and draw upon different underlying processing resources. [T]o completely analyze what we do when we read… would be to describe very many of the most intricate workings of the human mind, as well as to unravel the tangled story of the most remarkable specific performance that civilization has learned in all its history(Huey, 1908/1968, p. 3).

Electrophysiological evidence for a specific neural correlate of musical violation expectation in primary-school children

The majority of studies on music processing in children used simple musical stimuli. Here, primary schoolchildren judged the appropriateness of musical closure in expressive polyphone music, while high-density electroencephalography was recorded. Stimuli ended either regularly or contained refined in-key harmonic transgressions at closure. The children discriminated the transgressions well above chance. Regular and transgressed endings evoked opposite scalp voltage configurations peaking around 400ms after stimulus onset with bilateral frontal negativity for regular and centro-posterior negativity (CPN) for transgressed endings. A positive correlation could be established between strength of the CPN response and rater sensitivity (d-prime). We also investigated whether the capacity to discriminate the transgressions was supported by auditory domain specific or general cognitive mechanisms, and found that working memory capacity predicted transgression discrimination. Latency and distribution of the CPN are reminiscent of the N400, typically observed in response to semantic incongruities in language. Therefore our observation is intriguing, as the CPN occurred here within an intra-musical context, without any symbols referring to the external world. Moreover, the harmonic in-key transgressions that we implemented may be considered syntactical as they transgress structural rules. Such structural incongruities in music are typically followed by an early right anterior negativity (ERAN) and an N5, but not so here. Putative contributive sources of the CPN were localized in left pre-motor, mid-posterior cingulate and superior parietal regions of the brain that can be linked to integration processing. These results suggest that, at least in children, processing of syntax and meaning may coincide in complex intra-musical contexts.

The N400 and the fourth grade shift

While behavioral and educational data characterize a fourth grade shift in reading development, neuroscience evidence is relatively lacking. We used the N400 component of the event-related potential waveform to investigate the development of single word processing across the upper elementary years, in comparison to adult readers. We presented third graders, fourth graders, fifth graders, and college students with a well-controlled list of real words, pseudowords, letter strings, false font strings, and animal name targets. Words and pseudowords elicited similar N400s across groups. False font strings elicited N400s similar to words and letter strings in the three groups of children, but not in college students. The pattern of findings suggests relatively adult-like semantic and phonological processing by third grade, but a long developmental time course, beyond fifth grade, for orthographic processing in this context. Thus, the amplitude of the N400 elicited by various word-like stimuli does not reflect some sort of shift or discontinuity in word processing around the fourth grade. However, the results do suggest different developmental time courses for the processes that contribute to automatic single word reading and the integrative N400.

What changes in neural oscillations can reveal about developmental cognitive neuroscience: language development as a case in point

EEG is a primary method for studying temporally precise neuronal processes across the lifespan. Most of this work focuses on event related potentials (ERPs); however, using time-locked time frequency analysis to decompose the EEG signal can identify and distinguish multiple changes in brain oscillations underlying cognition (Bastiaansen et al., 2010). Further this measure is thought to reflect changes in inter-neuronal communication more directly than ERPs (Nunez and Srinivasan, 2006). Although time frequency has elucidated cognitive processes in adults, applying it to cognitive development is still rare. Here, we review the basics of neuronal oscillations, some of what they reveal about adult cognitive function, and what little is known relating to children. We focus on language because it develops early and engages complex cortical networks. Additionally, because time frequency analysis of the EEG related to adult language comprehension has been incredibly informative, using similar methods with children will shed new light on current theories of language development and increase our understanding of how neural processes change over the lifespan. Our goal is to emphasize the power of this methodology and encourage its use throughout developmental cognitive neuroscience.