Chronometry of visual word recognition during passive and lexical decision tasks: an ERP investigation

In order to investigate the neuroanatomical chronometry of word processing, two experiments using: Event-Related Potentials (ERPs) have been performed. The first one was designed to test the effects of orthographic, phonologic, and lexical properties of linguistic items on the pre-semantic components of ERPs during a passive reading task and massive repetition used to reduce familiarity effect between words and nonwords. In a second study, the level of familiarity was investigated by varying stimulus repetition and frequency in a lexical decision task. Overall results suggest a functional discrimination between orthographic and nonorthographic stimuli begun as early as 170 ms (N170 component) whereas the next components (N230 and N320) were sensitive to the orthographic nature of the stimuli, but also to their lexical/phonologic proprieties. The N320 associated to phonological processing (Bentin et al., 1999) was modulated by word frequency and massive repetition caused its disappearance. This suggests that this component may reflect a nonobligatory phonologic stage of grapheme-phoneme conversion postulated by the DRC model (Coltheart et al., 2001) or semantic phonologically mediated pathway (Harm & Seidenberg, in press).     

CHRONOMETRY OF VISUAL WORD RECOGNITION DURING PASSIVE AND LEXICAL DECISION TASKS: AN ERP INVESTIGATION

In order to investigate the neuroanatomical chronometry of word processing, two experiments using: Event Related Potentials (ERPs) have been performed. The first one was designed to test the effects of orthographic, phonologic, and lexical properties of linguistic items on the presemantic components of ERPs during a passive reading task and massive repetition used to reduce familiarity effect between words and nonwords. In a second study, the level of familiarity was investigated by varying stimulus repetition and frequency in a lexical decision task. Overall results suggest a functional discrimination between orthographic and nonorthographic stimuli begun as early as 170 ms (N170 component) whereas the next components (N230 and N320) were sensitive to the orthographic nature of the stimuli, but also to their lexical/phonologic proprieties. The N320 associated to phonological processing (Bentin et al., 1999) was modulated by word frequency and massive repetition caused its disappearance. This suggests that this component may reflect a nonobligatory phonologic stage of graphemephoneme conversion postulated by the DRC model (Coltheart et al., 2001) or semantic phonologically mediated pathway (Harm and Seidenberg, in press).     

Language distance in orthographic transparency affects cross‐language pattern similarity between native and non‐native languages

How native and non‐native languages are represented in the brain is one of the most important questions in neurolinguistics. Much research has found that the similarity in neural activity of native and non‐native languages are influenced by factors such as age of acquisition, language proficiency, and language exposure in the non‐native language. Nevertheless, it is still unclear how the similarity between native and non‐native languages in orthographic transparency, a key factor that affects the cognitive and neural mechanisms of phonological access, modulates the cross‐language similarity in neural activation and which brain regions show the modulatory effects of language distance in orthographic transparency. To address these questions, the present study used representational similarity analysis (RSA) to precisely estimate the neural pattern similarity between native language and two non‐native languages in Uyghur‐Chinese‐English trilinguals, whose third language (i.e., English) was more similar to the native language (i.e., Uyghur) in orthography than to their second language (i.e., Chinese). Behavioral results revealed that subjects responded faster to words in the non‐native language with more similar orthography to their native language in the word naming task. More importantly, RSA revealed greater neural pattern similarity between Uyghur and English than between Uyghur and Chinese in select brain areas for phonological processing, especially in the left hemisphere. Further analysis confirmed that those brain regions represented phonological information. These results provide direct neuroimaging evidence for the modulatory effect of language distance in orthographic transparency on cross‐language pattern similarity between native and non‐native languages during word reading.     

ERP manifestations of processing printed words at different psycholinguistic levels: time course and scalp distribution.

The aim of the present study was to examine the time course and scalp distribution of electrophysiological manifestations of the visual word recognition mechanism. Event-related potentials (ERPs) elicited by visually presented lists of words were recorded while subjects were involved in a series of oddball tasks. The distinction between the designated target and nontarget stimuli was manipulated to induce a different level of processing in each session (visual, phonological/phonetic, phonological/lexical, and semantic). The ERPs of main interest in this study were those elicited by nontarget stimuli. In the visual task the targets were twice as big as the nontargets. Words, pseudowords, strings of consonants, strings of alphanumeric symbols, and strings of forms elicited a sharp negative peak at 170 msec (N170); their distribution was limited to the occipito-temporal sites. For the left hemisphere electrode sites, the N170 was larger for orthographic than for nonorthographic stimuli and vice versa for the right hemisphere. The ERPs elicited by all orthographic stimuli formed a clearly distinct cluster that was different from the ERPs elicited by nonorthographic stimuli. In the phonological/phonetic decision task the targets were words and pseudowords rhyming with the French word vitrail, whereas the nontargets were words, pseudowords, and strings of consonants that did not rhyme with vitrail. The most conspicuous potential was a negative peak at 320 msec, which was similarly elicited by pronounceable stimuli but not by nonpronounceable stimuli. The N320 was bilaterally distributed over the middle temporal lobe and was significantly larger over the left than over the right hemisphere. In the phonological/lexical processing task we compared the ERPs elicited by strings of consonants (among which words were selected), pseudowords (among which words were selected), and by words (among which pseudowords were selected). The most conspicuous potential in these tasks was a negative potential peaking at 350 msec (N350) elicited by phonologically legal but not by phonologically illegal stimuli. The distribution of the N350 was similar to that of the N320, but it was broader and including temporo-parietal areas that were not activated in the "rhyme" task. Finally, in the semantic task the targets were abstract words, and the nontargets were concrete words, pseudowords, and strings of consonants. The negative potential in this task peaked at 450 msec. Unlike the lexical decision, the negative peak in this task significantly distinguished not only between phonologically legal and illegal words but also between meaningful (words) and meaningless (pseudowords) phonologically legal structures. The distribution of the N450 included the areas activated in the lexical decision task but also areas in the fronto-central regions. The present data corroborated the functional neuroanatomy of word recognition systems suggested by other neuroimaging methods and described their timecourse, supporting a cascade-type process that involves different but interconnected neural modules, each responsible for a different level of processing word-related information.     

Preserved visual language identification despite severe alexia

Patients with letter-by-letter alexia may have residual access to lexical or semantic representations of words despite severely impaired overt word recognition (reading). Here, we report a multilingual patient with severe letter-by-letter alexia who rapidly identified the language of written words and sentences in French and English while he had great difficulty in reading them, judging their lexical status or extracting semantic information. Lexical decision was strongly influenced by the orthographic structure of stimuli: whereas he easily determined the lexical status of illegal nonwords (e.g., 'rsdo'), he had random performance with legal pseudowords (e.g., 'binus'). When asked to determine the language of meaningless letter trigrams with high frequency in the English or French orthography (e.g., 'oth' or 'iqu') his performance was significantly above chance. In contrast, similarly to healthy participants his language decision was at chance with low-frequency trigrams. These findings suggest that written language identification relies on sublexical processing of orthographic rules specific to each language.     

Orthographic connectivity in Arabic reading: a case study of an individual with deep dyslexia and letter-by-letter reading

ABSTRACT

Arabic orthography is complex, partly as a consequence of variations in orthographic connectivity. In this article, we present the case study of CHS, an Arabic individual with deep dyslexia associated with letter-by-letter reading. In the experimental study, we specifically explored the influence of orthographic connectivity on CHS’s word recognition and reading abilities. Our results show that CHS’s performance was better preserved for words and non-words made up of connected letters than made up of non-connected letters. CHS demonstrated impairment of visuoperceptual mechanisms, which affected the processing of complex orthographic material. These results provide insight into the cognitive processes associated with reading Arabic.     

Effects of symbol type and numerical distance on the human event-related potential

This study investigated the influence of the symbol type and numerical distance of numbers on the amplitudes and peak latencies of event-related potentials (ERPs). Our aim was to (1) determine the point in time of magnitude information access in visual number processing; and (2) identify at what stage the advantage of Arabic digits over Chinese verbal numbers occur. ERPs were recorded from 64 scalp sites while subjects (n = 26) performed a classification task. Results showed that larger ERP amplitudes were elicited by numbers with distance-close condition in comparison to distance-far condition in the VPP component over centro-frontal sites. Furthermore, the VPP latency varied as a function of the symbol type, but the N170 did not. Such results demonstrate that magnitude information access takes place as early as 150 ms after onset of visual number stimuli and the advantage of Arabic digits over verbal numbers should be localized to the VPP component. We establish the VPP component as a critical ERP component to report in studies of numerical cognition and our results call into question the N170/VPP association hypothesis and the serial-stage model of visual number comparison processing.     

Access to numerical information is dependent on the modality of stimulus presentation in mental addition: a combined ERP and behavioral study

We investigated whether the mental representation of numbers is abstract amodal or modality-dependent. Subjects verified simple additions. In an event-related potential (ERP) experiment, subjects added an Arabic digit (S2) to a preceding number (S1) offsetting 3 s before S2. S1 was either a visually shown Arabic digit, a written number word or an acoustically presented number word. In a behavioral experiment, we measured the speed of addition using a modified paradigm. In the ERPs to S2, the amplitude of the parietal N1, the fronto-central P2, and the late positivity between 320 and 460 ms were more positive and RTs were faster when S1 was a heard number word than when S1 was a written number word. ERP amplitudes and reaction times took intermediate positions between the other two conditions when S1 was an Arabic digit. Between the Arabic and heard number conditions, this so-called numeral modality effect (NME) was present at electrodes Pz, P4, P3 and Cz when number size was small, whereas it was significant over electrode C4 and P4 when number size was large. Our results suggest that numbers presented in different surface-formats have differential access to number representations. Conclusions for models of number processing are drawn and the possible role of parietal number representations is discussed. We replicated the N270 ERP component and elicited the ERP numerical distance effect in response to incongruent arithmetical results.     

正常成人汉语句子识别的事件相关脑电位N400实验研究

目的探讨正常成人汉语句子结尾词匹配和非匹配事件相关脑电位（ERP）N400的特点。方法应用ERP仪,对58名19～63岁正常成人右利手受试者,进行汉语正常句子结尾词（匹配）与句子结尾歧义词（非匹配）N400的实验研究。结果正常成人中央区（Cz）、前额区（Fz）及顶区（Pz）脑区汉语句子结尾词匹配的N400平均潜伏期为364ms,平均波幅为8.9μV;非匹配的N400的平均潜伏期为409ms,平均波幅为12.9μV。正常成人各脑区匹配与非匹配的汉语句子结尾词的N400潜伏期、波幅比较有统计学差异。结论正常成人汉语句子识别的N400稳定、可靠;非匹配的汉语句子结尾词的N400潜伏期长,波幅高。     

Impact of orthographic transparency on typical and atypical reading development: Evidence in French-Spanish bilingual children

The present study aimed to quantify cross-linguistic modulations of the contribution of phonemic awareness skills and visual attention span (VA Span) skills (number of visual elements that can be processed simultaneously) to reading speed and accuracy in 18 Spanish-French balanced bilingual children with and without developmental dyslexia. The children were administered two similar reading batteries in French and Spanish. The deficits of the dyslexic children in reading accuracy were mainly visible in their opaque orthography (French) whereas difficulties indexed by reading speed were observed in both their opaque and transparent orthographies. Dyslexic children did not exhibit any phonemic awareness problems in French or in Spanish, but showed poor VA Span skills compared to their control peers. VA span skills correlated with reading accuracy and speed measures in both Spanish and French, whereas phonemic awareness correlated with reading accuracy only. Overall, the present results show that the VA Span is tightly related to reading speed regardless of orthographic transparency, and that it accounts for differences in reading performance between good and poor readers across languages. The present findings further suggest that VA Span skills may play a particularly important role in building-up specific word knowledge which is critical for lexical reading strategies.     

N300 indexes deficient integration of orthographic and phonological representations in children with dyslexia

In transparent orthographies, like German, children with developmental dyslexia (DD) are mainly characterized by a reading fluency deficit. The reading fluency deficit might be traced back to a scarce integration of orthographic and phonological representations. In order to address this question, the present study used EEG to investigate the N300, an ERP component which has been associated with the integration of orthographic and phonological representations. Twenty children without DD and 18 children with DD performed a phonological (P)-orthographic (O) matching task (P-O condition), which tapped the integration of orthographic and phonological representations. A control task was applied which did not require the integration of orthographic and phonological representations and consisted only of orthographic information (O-O condition). The O-O condition revealed a similar N300 distribution between groups with a bilateral activity over fronto-temporal electrodes. However, in the P-O condition N300 differentiated the 2 groups of children. The control group revealed greater activity over left fronto-temporal electrodes, whereas the N300 was distributed bilaterally in the group of children with DD suggesting deficient integration of orthographic and phonological representations. These findings might be related to the reading fluency deficit as it was also observed that better reading fluency was correlated with higher (r=-.36) and earlier peaking (r=-.33) N300 amplitudes in the left hemisphere and attenuated N300 amplitudes (r=.45) in the right hemisphere. Standardized low-resolution electromagnetic tomography analysis (sLORETA) revealed that children with DD rely more on right temporo-parietal brain areas compared to children without DD. Furthermore, in order to rule out that earlier deficient processes might influence the group differences found in the N300, we analyzed the N170 for group differences. We did not find significant differences between children without DD and children with DD. In conclusion the results suggest deficient integration of orthographic and phonological representations in dyslexia, as indexed by the N300, and further highlight how this activity is relevant for fluent reading.     

N170 ERPs could represent a logographic processing strategy in visual word recognition

Background  

Occipito-temporal N170 component represents the first step where face, object and word processing are discriminated along the ventral stream of the brain. N170 leftward asymmetry observed during reading has been often associated to prelexical orthographic visual word form activation. However, some studies reported a lexical frequency effect for this component particularly during word repetition that appears in contradiction with this prelexical orthographic step. Here, we tested the hypothesis that under word repetition condition, discrimination between words would be operated on visual rather than orthographic basis. In this case, N170 activity may correspond to a logographic processing where a word is processed as a whole.     

Working memory and lexical ambiguity resolution as revealed by ERPs: a difficult case for activation theories

This series of three event-related potential experiments explored the issue of whether the underlying mechanism of working memory (WM) supporting language processing is inhibitory or activational in nature. These different cognitive mechanisms have been proposed to explain the more efficient processing of subjects with a high WM span compared to those with a low WM span. Participants with high and low WM span were presented with sentences containing a homonym followed three words later by a nominal disambiguation cue and a final disambiguation using a verb. At the position of the disambiguation cue, inhibitory or activational WM mechanisms predict contrasting results. When activation is the underlying mechanism for efficient processing, the prediction is that high memory span persons activate both meanings of the homonym equally in WM, whereas low memory span persons only have one meaning present. When inhibition is the underlying mechanism, the predictions are the reverse. The ERP data, in particular, the variations of the meaning related N400 component, showed clear evidence for inhibition as the underlying cognitive mechanism in high-span readers. For low-span participants the cueing towards the dominant or the subordinate meaning elicited an equivalently large N400 component suggesting that both meanings are active in WM. In high-span subjects, the dominant disambiguation cue elicited a smaller N400 than the subordinate one, indicating that for these subjects particularly the dominant meaning is active. The experiments showed that inhibitory processes are probably underlying WM used during language comprehension in high-span subjects. Moreover, they demonstrate that these subjects can use their inhibition in a more flexible manner than low-span subjects. The effects that these processing differences have on the efficiency of language parsing are discussed.     

Word and pseudoword reading in children with specific speech and language impairment

Children with specific language impairment frequently encounter difficulties in learning to read and in particular, in word recognition. The present study set out to determine the precise impact of language impairment on word reading skills. We investigated single-word reading in 27 French children with specific speech and language impairment (2SLI). Precise quantification of reading levels in the 2SLI group showed an average delay of 3.5 years. Approximately 90% of these children were affected by a reading disorder, whereas for the remaining 10%, reading performance was within normal limits. Word reading procedures are analyzed using the so-called ‘dual route model’, which proposes that reading is achieved through two processes, the phonological and the orthographic procedures. Group comparison analyses of 27 reading level-matched control children, revealed an increased lexicality effect in the 2SLI group, indicating a specific deficit in the phonological procedure. Moreover, multiple case analyses revealed interindividual differences among the children with 2SLI, with four reading subtypes. Approximately 60% of these children reached the standard levels expected of younger children with identical reading levels (delayed reading profile) in both procedures. Twenty percent displayed qualitatively different reading mechanisms, with a greater deficit in the phonological procedure (phonological profile). These children showed a severe impairment in language production at the phonological level. Ten percent exhibited a greater orthographic deficit (surface profile) and 10% had normal reading skills (normal profile). Further research is required to improve our understanding of the relationships between 2SLI or specific language impairment and reading acquisition. The present results suggest that in clinical practice, both reading procedures should be exercised, with emphasis on the phonological procedure for children with more severe deficits in phonological production.     

III. Electrophysiological studies of face processing in Williams syndrome

Williams Syndrome (WMS) is a genetically based disorder characterized by pronounced variability in performance across different domains of cognitive functioning. This study examined brain activity linked to face-processing abilities, which are typically spared in individuals with WMS. Subjects watched photographic pairs of upright or inverted faces and indicated if the second face matched or did not match the first face. Results from a previous study with normal adults showed dramatic differences in the timing and distribution of ERP effects linked to recognition of upright and inverted faces. In normal adults, upright faces elicited ERP differences to matched vs. mismatched faces at approximately 320 msec (N320) after the onset of the second stimulus. This "N320" effect was largest over anterior regions of the right hemisphere. In contrast, the mismatch/match effect for inverted faces consisted of a large positive component between 400 and 1000 msec (P500) that was largest over parietal regions and was symmetrical. In contrast to normal adults, WMS subjects showed an N320-mismatch effect for both upright and inverted faces. Additionally, the WMS subjects did not display the N320 right-hemisphere asymmetry observed in the normal adults. WMS subjects also displayed an abnormally small negativity at 100 msec (N100) and an abnormally large negativity at 200 msec (N200) to both upright and inverted faces. This ERP pattern was observed in all subjects with WMS but was not observed in the normal controls. These results may be linked to increased attention to faces in subjects with WMS and might be specific to the disorder. These results were consistent with our ERP studies of language processing in WMS, which suggested abnormal cerebral specialization for spared cognitive functions in individuals with WMS.     

Function-Specific High-Probability "Nodes" Identified in Posterior Language Cortex

PURPOSE: Posterior, "Wenicke's," language areas have a high degree of between-subject variability, as shown by electrical-stimulation mapping. We investigated the possibility of an organized structure in the distribution of posterior language areas. METHODS: Extraoperative subdural grid stimulation was performed on 67 left hemisphere-dominant patients before resective epilepsy surgery during counting, naming, and reading. Intersubject-averaged language maps were generated in which stimulation disrupted only one language function and not the others, or combinations of language functions. RESULTS: Language sites, although highly variable between subjects, were not organized randomly and appeared to be arranged into several focal, non-contiguous, higher probability "nodes" devoted to different aspects of language processing. Speech-arrest sites were concentrated in classic Wernicke's area. Areas where stimulation induced only reading errors were found in the posterior middle temporal gyrus and the inferior parietal lobule. These regions may correspond with an orthographic input lexicon. Areas eliciting only naming errors were found in the posterior inferior temporal gyrus extending into the mid-middle temporal gyrus and may represent a visual-representation input lexicon. Sites where stimulation elicited errors in both naming and reading were more variable in location than sites devoted to only one function, extended farther anteriorly along the temporal neocortex, and may correspond with a semantic lexicon. CONCLUSIONS: The existence of high-probability nodes in posterior language cortex supports a modality-specific modular architecture and the possibility of a conserved, universal structure.     

Late acquisition of literacy in a native language

With event-related functional MRI (fMRI) and with behavioral measures we studied the brain processes underlying the acquisition of native language literacy. Adult dialect speakers were scanned while reading words belonging to three different conditions: dialect words, i.e., the native language in which subjects are illiterate (dialect), German words, i.e., the second language in which subjects are literate, and pseudo-words. Investigating literacy acquisition of a dialect may reveal how novel readers of a language build an orthographic lexicon, i.e., establish a link between already available semantic and phonological representations and new orthographic word forms. The main results of the study indicate that a set of regions, including the left anterior hippocampal formation and subcortical nuclei, is involved in the buildup of orthographic representations. The repeated exposure to written dialect words resulted in a convergence of the neural substrate to that of the language in which these subjects were already proficient readers. The latter result is compatible with a "fast" brain plasticity process that may be related to a shift of reading strategies.     

Altered hemispheric asymmetry during word processing in dyslexic children: an event-related potential study

The present event-related potential study aimed at finding neurophysiological correlates of inadequate reading performances in developmental dyslexia. By using the same set of words in different linguistic tasks, we found variations of cortical asymmetry between dyslexic individuals and controls starting with the N420, a component supposed to index the phonological processing during reading. Whereas in controls this component was left lateralized, in disabled readers it was more distributed across hemispheres. The observed lack of lateralization in dyslexic individuals was also found in the later slow negative wave that developed in the 700 to 1500-ms time interval. We postulate that the altered asymmetry is related to an impairment of the grapheme-phoneme conversion mechanism. The findings would therefore support the hypothesis of a phonological deficit underlying this learning disability.     

Magnetoencephalographic localization of the basal temporal language area

Magnetoencephalography (MEG) recordings were made on 25 native English-speaking patients with localization-related epilepsy during a semantic language task (verb generation). Eighteen right-handed subjects with normal reading ability had MEG scans performed during the same language task. MEG data was analyzed by MR-FOCUSS, a current density imaging technique. Detectable MEG signals arising from activation in the left fusiform gyrus, also known as the basal temporal language area (BTLA), occurred at 167 +/- 18 ms (n = 43) in all subjects. The BTLA has been associated with a variety of language production and comprehension tasks involving processing of semantic, orthographic, and phonologic information. MEG may become an important tool in efforts to further define the linguistic operations of specific regions within this language area.