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.

ERPs and morphological processing: the N400 and semantic composition.

Both behavioral and electrophysiological evidence suggests that fluent readers decompose morphologically complex words into their constituent parts. Previous event-related potential (ERP) research has been equivocal with regard to whether the N400 component indexes morphological decomposition or the integration of the products of decomposition, a process called semantic composition. In a visual lexical decision task with college students, we recorded ERPs to a well-controlled set of words and nonwords made up of bound morphemes (discern, predict; disject, percern) or free morphemes (cobweb, earring; cobline, bobweb) and monomorphemic control words and nonwords (garlic, minnow; gartus, buzlic). For each of the three morphological types, participants were faster to respond to words than to nonwords. Furthermore, for each of the three morphological types, the amplitude of the N400 was more negative to nonwords than to matched words, an effect indicating that the N400 is more sensitive to the lexicality of the whole stimulus than to the meaningfulness of the constituent parts of the stimulus. The N400 lexicality effect was not significantly different across the three morphological types. To our knowledge, this is the first ERP study to directly compare the processing of printed sets of words composed of bound and free morphemes and monomorphemic control stimuli in order to explore the relative sensitivity of the N400 to morphological decomposition (i.e., the status of the parts) and semantic composition (i.e., the status of the whole). Our findings are consistent with an interpretation of the N400 as an index of a process of semantic composition.

Auditory pseudoword rhyming effects in bilingual children reflect second language proficiency: An ERP study.

This study investigated second language (L2-English) phonological processing in 31 Spanish-English bilingual, 6- to 8-year-old schoolchildren in an event-related potential (ERP) auditory pseudoword rhyming paradigm. In addition, associations between ERP effects and L2 proficiency as measured by standardized tests of receptive language and receptive vocabulary were explored. We found a classic posterior ERP rhyming effect that was more widely distributed in children with higher L2 proficiency in group analyses and was larger for children with better L2 proficiency in correlation analyses. In contrast, the amplitude of an early (75-125 ms) auditory positivity was larger in children with lower L2 proficiency. This pattern suggests differential use of early and late auditory/phonological processing resources in the pseudoword rhyme task associated with L2 proficiency, which is consistent with the predictions of the lexical restructuring model in a bilingual context.

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.

When two vowels go walking: An ERP study of the vowel team rule.

In an event-related potential (ERP) study of the vowel team rule in American English ("when two vowels go walking, the first does the talking"), we used a visual lexical decision task to determine whether words that do (e.g., braid) and do not (e.g., cloud) follow the rule elicit different processing, and to determine if this extends to nonwords (e.g., braip, cloup). In 32 young adults, N1 amplitude distinguished between rule-following and rule-breaking items: N1 amplitude was more negative to rule-breaking words and nonwords. In contrast, there were no significant effects of vowel team rule adherence on N400 amplitude. Behaviorally, participants responded more quickly and accurately to rule-following words, a pattern not observed for nonwords. These findings demonstrate that adherence to the vowel team rule can be indexed by both neural and behavioral measures in fluently reading young adults.

An ERP study of cross-modal rhyming: Influences of phonology and orthography.

In a cross-modal rhyming study with visual pseudoword primes and auditory word targets, we found a typical ERP rhyming effect such that nonrhyming targets elicited a larger N400/N450 than rhyming targets. An orthographic effect was also apparent in the same 350- to 600-ms epoch as the phonological effect: The rhyming effect for targets with rime orthography that did not match their primes' (e.g., tain-"sane") was smaller over the left hemisphere than the rhyming effect for targets with rime orthography that did match their primes' (e.g., nain-"gain"), although the spellings of the auditory word targets were never explicitly shown. Our results indicate that this cross-modal ERP rhyming effect indexes both phonological and orthographic processing-for auditory stimuli for which no orthography is presented in the task. This pattern of findings is consistent with the notion of coactivation of sublexical orthography and phonology in fluent adult readers as they both read and listen.

Neural mechanisms of selective auditory attention are enhanced by computerized training: electrophysiological evidence from language-impaired and typically developing children.

Recent proposals suggest that some interventions designed to improve language skills might also target or train selective attention. The present study examined whether six weeks of high-intensity (100 min/day) training with a computerized intervention program designed to improve language skills would also influence neural mechanisms of selective auditory attention previously shown to be deficient in children with specific language impairment (SLI). Twenty children received computerized training, including 8 children diagnosed with SLI and 12 children with typically developing language. An additional 13 children with typically developing language received no specialized training (NoTx control group) but were tested and retested after a comparable time period to control for maturational and test-retest effects. Before and after training (or a comparable delay period for the NoTx control group), children completed standardized language assessments and an event-related brain potential (ERP) measure of selective auditory attention. Relative to the NoTx control group, children receiving training showed increases in standardized measures of receptive language. In addition, children receiving training showed larger increases in the effects of attention on neural processing following training relative to the NoTx control group. The enhanced effect of attention on neural processing represented a large effect size (Cohen's d=0.8), and was specific to changes in signal enhancement of attended stimuli. These findings indicate that the neural mechanisms of selective auditory attention, previously shown to be deficient in children with SLI, can be remediated through training and can accompany improvements on standardized measures of language.

Three kinds of rhymes: An ERP study.

In a simple prime-target visual rhyming paradigm, pairs of words, nonwords, and single letters elicited similar event-related potential (ERP) rhyming effects in young adults. Within each condition, primes elicited contingent negative variation (CNV) while nonrhyming targets elicited more negative waveforms than rhyming targets within the 320-500ms (N400/N450) time window. The target rhyming effect, apparently primarily an index of phonological processing, was similar across conditions but tended to be smaller in mean amplitude for letters. One of the first reports of such a letter rhyming effect in the ERP literature, these findings could be important developmentally because letter rhyme tasks simultaneously index the two best predictors of ease of learning to read: letter name knowledge and phonological awareness.

A Picture Is Worth Both Spelling and Sound.

In an event-related potential (ERP) study using picture stimuli, we explored whether spelling information is co-activated with sound information even when neither type of information is explicitly provided. Pairs of picture stimuli presented in a rhyming paradigm were varied by both phonology (the two images in a pair had either rhyming, e.g., boat and goat, or non-rhyming, e.g., boat and cane, labels) and orthography (rhyming image pairs had labels that were either spelled the same, e.g., boat and goat, or not spelled the same, e.g., brain and cane). Electrophysiological picture rhyming (sound) effects were evident in terms of both N400/N450 and late effect amplitude: Non-rhyming images elicited more negative waves than rhyming images. Remarkably, the magnitude of the late ERP rhyming effect was modulated by spelling - even though words were neither explicitly seen nor heard during the task. Moreover, both the N400/N450 and late rhyming effects in the spelled-the-same (orthographically matched) condition were larger in the group with higher scores (by median split) on a standardized measure of sound awareness. Overall, the findings show concomitant meaning (semantic), sound (phonological), and spelling (orthographic) activation for picture processing in a rhyming paradigm, especially in young adults with better reading skills. Not outwardly lexical but nonetheless modulated by reading skill, electrophysiological picture rhyming effects may be useful for exploring co-activation in children with dyslexia.

Dissociating frequency and animacy effects in visual word processing: An fMRI study.

In an fMRI investigation of the neural representation of word frequency and animacy, participants read high- and low-frequency words within living and nonliving semantic categories. Both temporal (left fusiform gyrus) and parietal (left supramarginal gyrus) activation patterns differentiated between animal and tool words after controlling for frequency. Activation patterns in a smaller ventral temporal region, a subset of the voxels identified in the animacy contrast, differentiated between high- and low-frequency words after controlling for animacy. Activation patterns in the larger temporal region distinguished between high- and low-frequency words just as well as patterns within the smaller region. However, in analyses by animacy category, frequency effects in these temporal regions were significant only for tool, not for animal, words. Thus, lexical word frequency information and semantic animacy category information are conjointly represented in left fusiform gyrus activation patterns for some, but not all, concrete nouns.

Anterior and posterior erp rhyming effects in 3- to 5-year-old children.

During early literacy skills development, rhyming is an important indicator of the phonological precursors required for reading. To determine if neural signatures of rhyming are apparent in early childhood, we recorded event-related potentials (ERPs) from 3- to 5-year-old, preliterate children (N = 62) in an auditory prime-target nonword rhyming paradigm (e.g., bly-gry, blane-vox). Overall, nonrhyming targets elicited a larger negativity (N450) than rhyming targets over posterior regions. In contrast, rhyming targets elicited a larger negativity than nonrhyming targets over fronto-lateral sites. The amplitude of the two rhyming effects was correlated, such that a larger posterior effect occurred with a smaller anterior effect. To determine whether these neural signatures of rhyming related to phonological awareness, we divided the children into two groups based on phonological awareness scores while controlling for age and socioeconomic status. The posterior rhyming effect was stronger and more widely distributed in the group with better phonological awareness, whereas differences between groups for the anterior effect were small and not significant. This pattern of results suggests that the rhyme processes indexed by the anterior effect are developmental precursors to those indexed by the posterior effect. Overall, these findings demonstrate early establishment of distributed neurocognitive networks for rhyme processing.

Bridges over troubled waters: education and cognitive neuroscience.

Recently there has been growing interest in and debate about the relation between cognitive neuroscience and education. Our goal is to advance the debate beyond both recitation of potentially education-related cognitive neuroscience findings and the claim that a bridge between fields is chimerical. In an attempt to begin a dialogue about mechanisms among students, educators, researchers and practitioner-scientists, we propose that multiple bridges can be built to make connections between education and cognitive neuroscience, including teacher training, researcher training and collaboration. These bridges--concrete mechanisms that can advance the study of mind, brain and education--will benefit both educators and cognitive neuroscientists, who will gain new perspectives for posing and answering crucial questions about the learning brain.

Selective auditory attention in 3- to 5-year-old children: an event-related potential study.

Behavioral and electrophysiological evidence suggests that the development of selective attention extends over the first two decades of life. However, much of this research may underestimate the attention abilities of young children. By providing strong, redundant attention cues, we show that sustained endogenous selective attention has similar effects on ERP indices of auditory processing in adults and children as young as 3 years old. All participants were cued to selectively attend to one of two simultaneously presented stories that differed in location (left/right), voice (male/female), and content. The morphology of the ERP waveforms elicited by probes embedded in the stories was very different for adults, who showed a typical positive-negative-positive pattern in the 300 ms after probe onset, and children, who showed a single broad positivity during this epoch. However, for 3- to 5-year-olds, 6- to 8-year-olds, and adults, probes in the attended story elicited larger amplitude ERPs beginning around 100 ms after probe onset. This attentional modulation of exogenously driven components was longer in duration for the youngest children. In addition, attended linguistic probes elicited a larger negativity 300-500 ms for all groups, indicative of additional attentional processing. These data show that with adequate cues, even children as young as 3 years old can selectively attend to one auditory stream while ignoring another and that doing so alters auditory sensory processing at an early stage. Furthermore, they suggest that the neural mechanisms by which selective attention affects auditory processing are remarkably adult-like by this age.

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

In an investigation of the development of fine-tuning for word processing across the late elementary school years as indexed by the posterior N1 and P2 components of the ERP waveform, third, fourth, and fifth graders and a comparison group of adults viewed words, pseudowords, nonpronounceable letter strings, and false font strings in a semantic categorization task. In adults, N1 was larger to and P2 was later to words as compared to pseudowords, a finely tuned effect of lexicality reflecting specialization for word processing. In contrast, in each group of children, N1 was larger to letter strings than false font strings and P2 was larger to false font strings than letter strings, reflecting coarse encoding for orthography. In regression analyses, scores on standardized behavioral test measures of orthographic knowledge, decoding skill, and fluency predicted N1 amplitude; these effects were not significant with age included as a separate predictor. None of the behavioral scores, in models including or not including age, predicted P2 amplitude. In direct comparisons between groups, there were multiple differences between the child and adult groups for both N1 and P2 amplitude effects, and only a single significant difference between two child groups. Overall, the findings suggest a lengthy developmental time course for the fine-tuning of early word processing as indexed by N1 and P2.

The N400 elicited by homonyms in puns: Two primes are not better than one.

To comprehend a pun involving a homonym (e.g., The prince with a bad tooth got a crown), both meanings of the homonym must be accessed and selected. Previous ERP studies have shown that the N400 reflects lexicosemantic processing, but none have directly investigated the N400 elicited by homonyms in the unique context of puns. Here, N400 priming effects showed that the dual context of puns (e.g., the primes prince and tooth) did not facilitate homonym processing in comparison to single dominant biasing (e.g., The prince with a bad leg got a crown) or subordinate biasing (e.g., The adult with a bad tooth got a crown) conditions. However, homonyms did elicit a less negative N400 (i.e., priming) in the pun condition in comparison to the neutral context condition (e.g., The adult with a bad leg got a crown). These findings are interpreted in terms of the dominant advantage and subordinate bias effect posited by the reordered access model of homonym processing, and in terms of N400 amplitude as an index of how consistently various sources of semantic featural information converge on one lexical item, even when two lexical items must be activated for comprehension.

Auditory and visual refractory period effects in children and adults: an ERP study.

OBJECTIVE: This developmental study was designed to investigate event-related potential (ERP) refractory period effects in the auditory and visual modalities in children and adults and to correlate these electrophysiological measures with standard behavioral measures. METHODS: ERPs, accuracy, and reaction time were recorded as school-age children and adults monitored a stream of repetitive standard stimuli and detected occasional targets. Standards were presented at various interstimulus intervals (ISIs) in order to measure refractory period effects on early sensory components. RESULTS: As has been reported previously in adults, larger components for standards with longer ISIs were observed for an auditory N1 and the visual occipital P1 and P2 in adults. Remarkably similar effects were observed in children. However, only children showed refractory effects on the amplitude of the visual N1 and P2 measured at anterior sites. Across groups, behavioral accuracy and reaction time were correlated with latencies of auditory N1 and visual P2 across ISI conditions. CONCLUSIONS: The results establish a normal course of development for auditory and visual ERP refractory period effects across the 6- to 8-year-old age range and indicate similar refractoriness in the neural systems indexed by ERPs in these paradigms in typically developing children and adults. Further, the results suggest that electrophysiological measures and standard behavioral measures may at least in part index similar processing in the present paradigms. SIGNIFICANCE: These findings provide a foundation for further investigation into atypical development, particularly in those populations for which processing time deficits have been implicated such as children with specific language impairment or dyslexia.

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).

Word and picture processing in children: an event-related potential study.

In an investigation of the N400 component, event-related potentials (ERPs) elicited by 4 types of word stimuli (real words, pseudowords, random letter strings, and false fonts) and 3 types of picture stimuli (real pictures, pseudopictures, and picture parts) presented in separate lists were recorded from 10- and 11-year-old children. All types of word stimuli elicited an anteriorly distributed negativity peaking at about 400 msec (antN400). Words and pseudowords elicited similar ERPs, whereas ERPs to letter strings differed from those to both pseudowords and false fonts. All types of picture stimuli elicited dual anterior negativities (N350 and N430). Real pictures and pseudopictures elicited similar ERPs, whereas pseudopictures and picture parts elicited asymmetrical processing. The results are discussed in terms of increased sensitivity to and dependence on context in children.

Imagining the truth and the moon: an electrophysiological study of abstract and concrete word processing.

Previous event-related potential studies have indicated that both a widespread N400 and an anterior N700 index differential processing of concrete and abstract words, but the nature of these components in relation to concreteness and imagery has been unclear. Here, we separated the effects of word concreteness and task demands on the N400 and N700 in a single word processing paradigm with a within-subjects, between-tasks design and carefully controlled word stimuli. The N400 was larger to concrete words than to abstract words, and larger in the visualization task condition than in the surface task condition, with no interaction. A marked anterior N700 was elicited only by concrete words in the visualization task condition, suggesting that this component indexes imagery. These findings are consistent with a revised or extended dual coding theory according to which concrete words benefit from greater activation in both verbal and imagistic systems.