Electrophysiological measures of language processing in bilinguals

Transcranial photobiomodulation on the left inferior frontal gyrus enhances Mandarin Chinese L1 and L2 complex sentence processing performances

This study investigated the causal enhancing effect of transcranial photobiomodulation (tPBM) over the left inferior frontal gyrus (LIFG) on syntactically complex Mandarin Chinese first language (L1) and second language (L2) sentence processing performances. Two (L1 and L2) groups of participants (thirty per group) were recruited to receive the double-blind, sham-controlled tPBM intervention via LIFG, followed by the sentence processing, the verbal working memory (WM), and the visual WM tasks. Results revealed a consistent pattern for both groups: (a) tPBM enhanced sentence processing performance but not verbal WM for linear processing of unstructured sequences and visual WM performances; (b) Participants with lower sentence processing performances under sham tPBM benefited more from active tPBM. Taken together, the current study substantiated that tPBM enhanced L1 and L2 sentence processing, and would serve as a promising and cost-effective noninvasive brain stimulation (NIBS) tool for future applications on upregulating the human language faculty.

Processing reduced speech in the L1 and L2: a combined eye-tracking and ERP study

We examined the cognitive processes underlying the comprehension of reduced word pronunciation variants in natives and advanced learners of French. In a passive listening visual world task, participants heard sentences containing either a reduced or a full form and saw pictures representing the target word, a phonological competitor and two neutral distractors. After each sentence they saw a picture and had to decide whether it matched the content of that sentence. Eye movements and EEG were recorded simultaneously. Because the two recordings offer complementary information about cognitive processes, we developed methods for analysing the signals in combination. We found a stronger effect of reduction on phonetic processing and semantic integration in learners than in natives, but the effects are different from the N100/N400 and P600 effects found in previous research. Time-locking EEG signals on fixation moments in the eye movements offers a window onto the time course of semantic integration.

Can Speaking More Than One Language Help Prevent Alzheimer's Disease?

Alzheimer's disease (AD) is an age-related neurocognitive disorder that is epidemic in the elderly population. Currently, there are limited pharmacological interventions, and this has heightened the urgency to identify potential preventable or modifiable risk factors that promote resilience to the neuropathological effects of AD. The regular use of two or more languages is one such factor that may increases cognitive reserve through the long-standing executive control involved in managing multiple languages in the brain. There is also evidence that bilingualism is associated with increased brain reserve or maintenance, particularly in frontal-executive structures and networks. This review examines the current, sometimes conflicting literature on bi/multilingualism and AD. These studies have confounding variations in the assessment of age of second language onset, language proficiency, language usage, and whether determining incidence of AD or age of symptom onset. Despite these limitations, most publications support the presence of increased frontal-executive reserve that compensates for the development of AD neuropathology and, thereby, delays the emergence of clinical symptoms of dementia by about 4-5 years. Although regularly speaking more than one language does not protect against AD neuropathology, the delay in its clinical expression has a potentially significant impact on the lifelong morbidity from this age-related disease. Learning other languages may be an important modifiable factor for delaying the clinical expression of AD in later life.

Comprehending scientific metaphors in the bilingual brain: Evidence from event-related potentials

While the processing mechanisms of novel and conventional metaphors were widely investigated in previous monolingual studies, little attention has been devoted to how metaphoric utterances are processed by the bilingual brain as well as how scientific context might modulate such processes. Using event-related potentials (ERPs), this paper investigates the way in which scientific metaphors are electrophysiologically processed in Chinese (L1) and English (L2), with the aim of investigating the different mechanisms for understanding metaphorical language in first (L1) and second (L2) languages. By time-locking the N400 and later LPC time windows, the research show how meaning integration differs between L1 and L2 at different stages when comprehending figurative language. We found that compared with Chinese scientific metaphors, English scientific metaphors elicited greater N400, smaller late positive component (LPC), and greater late negativity, and English literals elicited greater late negativity. Our findings suggest that the dynamics of processing figurative meaning in bilingual brains over time show a complex pattern, with language, context, inference and salience jointly modulating temporal dynamics and possible cerebral asymmetries, supporting the revised hierarchical model.

Agents Strongly Preferred: ERP Evidence from Natives and Non-Natives Processing Intransitive Sentences in Spanish

Are non-native speakers able to process their second language in a native-like way? The present study used the Event-Related Potentials’ (ERPs) method to address this issue by focusing (1) on agent vs. agentless intransitive sentences and (2) on person vs. number agreement morphology. For that purpose, native and high proficiency and early non-native speakers of Spanish were tested while processing intransitive sentences containing grammatical and ungrammatical subject–verb agreement. Results reveal greater accuracy in the agent (unergative) condition as compared with the agentless (unaccusative) condition and different ERP patterns for both types of verbs in all participants, suggesting a larger processing cost for the agentless sentences than for the agentive ones. These effects were more pronounced in the native group as compared with the non-native one in the early time window (300–500 ms). Differences between person and number agreement processing were also found at both behavioral and electrophysiological levels, indicating that those morphological features are distinctively processed. Importantly, this pattern of results held for both native and non-native speakers, thus suggesting that native-like competence is attainable given early Age of Acquisition (AoA), frequent use and high proficiency.

Bilingual Processing Mechanisms of Scientific Metaphors and Conventional Metaphors: Evidence via a Contrastive Event-Related Potentials Study

To study the different mechanisms of understanding figurative language in a speaker’s native language (L1) and their second language (L2), this study investigated how scientific metaphors in Chinese (L1) and English (L2) are electrophysiologically processed via event-related potential experimentation. Compared with the metaphors from daily life or in literary works, scientific metaphors tend to involve both a more complicated context structure and a distinct knowledge-inferencing process. During the N400 time window (300–500 ms), English scientific metaphors elicited more negative N400s than Chinese ones at the parietal region. In the late positive component (LPC) time window (550–800 ms), English scientific metaphors elicited less positive LPCs than Chinese ones at the parietal region, and larger late negativities encompassing smaller areas of the brain. The findings might indicate that for late unbalanced bilingual speakers, L2 scientific metaphor comprehension requires more effort in information retrieval or access to the non-literal route. Altogether, the possible findings are that non-native and non-dominant language processing involves decreased automaticity of cognitive mechanisms, and decreased sensitivity to the levels of conventionality of metaphoric meanings.

In a Bilingual Mood: Mood Affects Lexico-Semantic Processing Differently in Native and Non-Native Languages

Positive and negative moods tend to have differential effects on lexico-semantic processing in the native language (L1). Though accumulating evidence points to dampened sensitivity to affective stimuli in the non-native language (L2), little is known about the effects of positive and negative moods on L2 processing. Here, we show that lexico-semantic processing is differently affected by positive and negative moods only in L1. Unbalanced Polish–English bilinguals made meaningfulness judgments on L1 and L2 sentences during two EEG recording sessions featuring either positive- or negative-mood-inducing films. We observed a reduced N1 (lexical processing) for negative compared to positive mood in L2 only, a reduced N2 (lexico-semantic processing) in negative compared to positive mood in L1 only, a reduced N400 (lexico-semantic processing) for meaningless compared to meaningful L1 sentences in positive mood only, and an enhanced late positive complex (semantic integration and re-analysis) for L2 compared to L1 meaningful sentence in negative mood only. Altogether, these results suggest that positive and negative moods affect lexical, lexico-semantic, and semantic processing differently in L1 and L2. Our observations are consistent with previous accounts of mood-dependent processing and emotion down-regulation observed in bilinguals.

Current exposure to a second language modulates bilingual visual word recognition: An EEG study

Bilingual word recognition has been the focus of much empirical work, but research on potential modulating factors, such as individual differences in L2 exposure, are limited. This study represents a first attempt to determine the impact of L2-exposure on bilingual word recognition in both languages. To this end, highly fluent bilinguals were split into two groups according to their L2-exposure, and performed a semantic categorisation task while recording their behavioural responses and electro-cortical (EEG) signal. We predicted that lower L2-exposure should produce less efficient L2 word recognition processing at the behavioural level, alongside neurophysiological changes at the early pre-lexical and lexical levels, but not at a post-lexical level. Results confirmed this hypothesis in accuracy and in the N1 component of the EEG signal. Precisely, bilinguals with lower L2-exposure appeared less accurate in determining semantic relatedness when target words were presented in L2, but this condition posed no such problem for bilinguals with higher L2-exposure. Moreover, L2-exposure modulates early processes of word recognition not only in L2 but also in L1 brain activity, thus challenging a fully non-selective access account (cf. BIA + model, Dijkstra and van Heuven, 2002). We interpret our findings with reference to the frequency-lag hypothesis (Gollan et al., 2011).

Unexpected words or unexpected languages? Two ERP effects of code-switching in naturalistic discourse

Bilingual speakers often switch between languages in conversation without any advance notice. Psycholinguistic research has found that these language shifts (or code-switches) can be costly for comprehenders in certain situations. The present study explores the nature of these costs by comparing code-switches to other types of unexpected linguistic material. To do this, we used a novel EEG paradigm, the Storytime task, in which we record readings of natural texts, and then experimentally manipulate their properties by splicing in words. In this study, we manipulated the language of our target words (English, Spanish) and their fit with the preceding context (strong-fit, weak-fit). If code-switching incurs a unique cost beyond that incurred by an unexpected word, then we should see an additive pattern in our ERP indices. If an effect is driven by lexical expectation alone, then there should be a non-additive interaction such that all unexpected forms incur a similar cost. We found three effects: a general prediction effect (a non-additive N400), a post-lexical recognition of the switch in languages (an LPC for code-switched words), and a prolonged integration difficulty associated with weak-fitting words regardless of language (a sustained negativity). We interpret these findings as suggesting that the processing difficulties experienced by bilinguals can largely be understood within more general frameworks for understanding language comprehension. Our findings are consistent with the broader literature demonstrating that bilinguals do not have two wholly separate language systems but rather a single language system capable of using two coding systems.

Lifelong Bilingualism Functions as an Alternative Intervention for Cognitive Reserve Against Alzheimer's Disease

Bilingualism has been reported to significantly delay the onset of dementia and plays an important role in the management of Alzheimer's disease (AD), a condition inducing impairment in the brain network and cognitive decline. Cognitive reserve is associated with the adaptive maintenance of neural functions by protecting against neuropathology. Bilingualism acts as a beneficial environmental factor contributing to cognitive reserve, although some potential confounding variables still need further elucidation. In this article, the relationship between bilingualism and cognitive reserve is discussed, interpreting the advantage of bilingualism in protecting against cognitive decline. In addition, the possible brain and biochemical mechanisms, supporting the advantageous effects of bilingualism in delaying the onset of dementia, involved in bilingualism are reviewed. Effectively, bilingualism can be considered as a pharmacological intervention with no side effects. However, the investigation of the pharmacological parameters of bilingualism is still at an early stage.

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.

To electrify bilingualism: Electrophysiological insights into bilingual metaphor comprehension

Though metaphoric language comprehension has previously been investigated with event-related potentials, little attention has been devoted to extending this research from the monolingual to the bilingual context. In the current study, late proficient unbalanced Polish (L1)–English (L2) bilinguals performed a semantic decision task to novel metaphoric, conventional metaphoric, literal, and anomalous word pairs presented in L1 and L2. The results showed more pronounced P200 amplitudes to L2 than L1, which can be accounted for by differences in the subjective frequency of the native and non-native lexical items. Within the early N400 time window (300–400 ms), L2 word dyads evoked delayed and attenuated amplitudes relative to L1 word pairs, possibly indicating extended lexical search during foreign language processing, and weaker semantic interconnectivity for L2 compared to L1 words within the memory system. The effect of utterance type was observed within the late N400 time window (400–500 ms), with smallest amplitudes evoked by literal, followed by conventional metaphoric, novel metaphoric, and anomalous word dyads. Such findings are interpreted as reflecting more resource intensive cognitive mechanisms governing novel compared to conventional metaphor comprehension in both the native and non-native language. Within the late positivity time window (500–800 ms), Polish novel metaphors evoked reduced amplitudes relative to literal utterances. In English, on the other hand, this effect was observed for both novel and conventional metaphoric word dyads. This finding might indicate continued effort in information retrieval or access to the non-literal route during novel metaphor comprehension in L1, and during novel and conventional metaphor comprehension in L2. Altogether, the present results point to decreased automaticity of cognitive mechanisms engaged in non-native and non-dominant language processing, and suggest a decreased sensitivity to the levels of conventionality of metaphoric meanings in late proficient unbalanced bilingual speakers.

An Event Related Field Study of Rapid Grammatical Plasticity in Adult Second-Language Learners

The present study used magnetoencephalography (MEG) to investigate how Spanish adult learners of Basque respond to morphosyntactic violations after a short period of training on a small fragment of Basque grammar. Participants (n = 17) were exposed to violation and control phrases in three phases (pretest, training, generalization-test). In each phase participants listened to short Basque phrases and they judged whether they were correct or incorrect. During the pre-test and generalization-test, participants did not receive any feedback. During the training blocks feedback was provided after each response. We also ran two Spanish control blocks before and after training. We analyzed the event-related magnetic- field (ERF) recorded in response to a critical word during all three phases. In the pretest, classification was below chance and we found no electrophysiological differences between violation and control stimuli. Then participants were explicitly taught a Basque grammar rule. From the first training block participants were able to correctly classify control and violation stimuli and an evoked violation response was present. Although the timing of the electrophysiological responses matched participants' L1 effect, the effect size was smaller for L2 and the topographical distribution differed from the L1. While the L1 effect was bilaterally distributed on the auditory sensors, the L2 effect was present at right frontal sensors. During training blocks two and three, the violation-control effect size increased and the topography evolved to a more L1-like pattern. Moreover, this pattern was maintained in the generalization test. We conclude that rapid changes in neuronal responses can be observed in adult learners of a simple morphosyntactic rule, and that native-like responses can be achieved at least in small fragments of second language.

ERP Response Unveils Effect of Second Language Manipulation on First Language Processing

Lexical access in bilinguals has been considered either selective or non-selective and evidence exists in favor of both hypotheses. We conducted a linguistic experiment to assess whether a bilingual’s language mode influences the processing of first language information. We recorded event related potentials during a semantic priming paradigm with a covert manipulation of the second language (L2) using two types of stimulus presentations (short and long). We observed a significant facilitation of word pairs related in L2 in the short version reflected by a decrease in N400 amplitude in response to target words related to the English meaning of an inter-lingual homograph (homograph-unrelated group). This was absent in the long version, as the N400 amplitude for this group was similar to the one for the control-unrelated group. We also interviewed the participants whether they were aware of the importance of L2 in the experiment. We conclude that subjects participating in the long and short versions were in different language modes: closer to monolingual mode for the long and closer to bilingual mode for the short version; and that awareness about covert manipulation of L2 can influence the language mode, which in its turn influences the processing of the first language.

Commonality of neural representations of sentences across languages: Predicting brain activation during Portuguese sentence comprehension using an English-based model of brain function

The aim of the study was to test the cross-language generative capability of a model that predicts neural activation patterns evoked by sentence reading, based on a semantic characterization of the sentence. In a previous study on English monolingual speakers (Wang et al., submitted), a computational model performed a mapping from a set of 42 concept-level semantic features (Neurally Plausible Semantic Features, NPSFs) as well as 6 thematic role markers to neural activation patterns (assessed with fMRI), to predict activation levels in a network of brain locations. The model used two types of information gained from the English-based fMRI data to predict the activation for individual sentences in Portuguese. First, it used the mapping weights from NPSFs to voxel activation levels derived from the model for English reading. Second, the brain locations for which the activation levels were predicted were derived from a factor analysis of the brain activation patterns during English reading. These meta-language locations were defined by the clusters of voxels with high loadings on each of the four main dimensions (factors), namely people, places, actions and feelings, underlying the neural representations of the stimulus sentences. This cross-language model succeeded in predicting the brain activation patterns associated with the reading of 60 individual Portuguese sentences that were entirely new to the model, attaining accuracies reliably above chance level. The prediction accuracy was not affected by whether the Portuguese speaker was monolingual or Portuguese-English bilingual. The model's confusion errors indicated an accurate capture of the events or states described in the sentence at a conceptual level. Overall, the cross-language predictive capability of the model demonstrates the neural commonality between speakers of different languages in the representations of everyday events and states, and provides an initial characterization of the common meta-language neural basis.

Genetic predictor of working memory and prefrontal function in women with HIV

The Val158Met (rs4680) single-nucleotide polymorphism (SNP) of the catechol-O-methyltransferase gene (COMT) influences executive function and prefrontal function through its effect on dopamine (DA) metabolism. Both HIV and the Val allele of the Val158Met SNP are associated with compromised executive function and inefficient prefrontal function. The present study used behavioral and neuroimaging techniques to determine independent and interactive associations between HIV serostatus and COMT genotype on working memory and prefrontal function in women. For the behavioral study, 54 HIV-infected and 33 HIV-uninfected women completed the 0-, 1-, and 2-back conditions of the verbal N-back, a working memory test. For the imaging study, 36 women (23 HIV-infected, 13 HIV-uninfected) underwent functional magnetic resonance imaging (fMRI) assessments while completing the N-back task. HIV-infected women demonstrated significantly worse N-back performance compared with HIV-uninfected women (p < 0.05). A significant serostatus by genotype interaction (p < 0.01) revealed that, among Val/Val, but not Met allele carriers, HIV-infected women performed significantly worse than HIV-uninfected controls across N-back conditions (p < 0.01). Analogous to behavioral findings, a serostatus by genotype interaction revealed that HIV-infected Val/Val carriers showed significantly greater prefrontal activation compared with HIV-uninfected Val/Val carriers (p < 0.01). Conversely, HIV-uninfected Met allele carriers demonstrated significantly greater prefrontal activation compared with HIV-infected Met allele carriers. Findings suggest that the combination of HIV infection and the Val/Val COMT genotype leads to working memory deficits and altered prefrontal function in HIV-infected individuals.

Development of neural systems for reading in the monolingual and bilingual brain: new insights from functional near infrared spectroscopy neuroimaging

What neural changes underlie reading development in monolingual and bilingual children? We examined neural activation patterns of younger (ages 6-8) and older (ages 8-10) children and adults to see whether early-life language experience influences the development of neural systems for reading. Using functional Near Infrared Spectroscopy, we observed an age-related shift in neural recruitment of language areas (left inferior frontal gyrus [LIFG], superior temporal gyrus [STG]). Bilinguals showed a greater extent and variability of neural activation in bilateral IFG and STG, and higher cognitive areas (dorsolateral prefrontal cortex, rostrolateral prefrontal cortex). This bilingual "neural signature" reveals the extent that neural systems underlying reading development can be modified through differences in early-life language experience.

An ERP study on initial second language vocabulary learning

This study examined the very initial phases of orthographic and semantic acquisition in monolingual native English speakers learning Chinese words under controlled laboratory conditions. Participants engaged in 10 sessions of vocabulary learning, four of which were used to obtain ERPs. Performance in behavioral tests improved over sessions, and these data were used to define fast and slow learners. Most important is that ERPs in the two groups of learners revealed qualitatively distinct learning patterns. Only fast learners showed a left-lateralized increase in N170 amplitude with training. Furthermore, only fast learners showed an increased N400 amplitude with training, with a distinct anterior distribution. Slow learners, on the other hand, showed a posterior positive effect, with increasingly positive-going waveforms in occipital sites as training progressed. Possible mechanisms underlying these qualitative differences are discussed.

How age of bilingual exposure can change the neural systems for language in the developing brain: a functional near infrared spectroscopy investigation of syntactic processing in monolingual and bilingual children

•

Early life bilingual language experience can change the developing brain.

•

Age of first bilingual exposure predicts neural activation for language.

•

Bilinguals show greater extent and variability of neural activity in language areas.

•

Early-exposed bilinguals show greater activation in IFG and STG vs. monolinguals.

•

Later-exposed bilinguals have greater DLPFC activity vs. early bilinguals.

Is the developing bilingual brain fundamentally similar to the monolingual brain (e.g., neural resources supporting language and cognition)? Or, does early-life bilingual language experience change the brain? If so, how does age of first bilingual exposure impact neural activation for language?

We compared how typically-developing bilingual and monolingual children (ages 7–10) and adults recruit brain areas during sentence processing using functional Near Infrared Spectroscopy (fNIRS) brain imaging. Bilingual participants included early-exposed (bilingual exposure from birth) and later-exposed individuals (bilingual exposure between ages 4–6).

Both bilingual children and adults showed greater neural activation in left-hemisphere classic language areas, and additionally, right-hemisphere homologues (Right Superior Temporal Gyrus, Right Inferior Frontal Gyrus). However, important differences were observed between early-exposed and later-exposed bilinguals in their earliest-exposed language. Early bilingual exposure imparts fundamental changes to classic language areas instead of alterations to brain regions governing higher cognitive executive functions. However, age of first bilingual exposure does matter. Later-exposed bilinguals showed greater recruitment of the prefrontal cortex relative to early-exposed bilinguals and monolinguals.

The findings provide fascinating insight into the neural resources that facilitate bilingual language use and are discussed in terms of how early-life language experiences can modify the neural systems underlying human language processing.

Differences in word recognition between early bilinguals and monolinguals: behavioral and ERP evidence

We investigated the behavioral and brain responses (ERPs) of bilingual word recognition to three fundamental psycholinguistic factors, frequency, morphology, and lexicality, in early bilinguals vs. monolinguals. Earlier behavioral studies have reported larger frequency effects in bilinguals' nondominant vs. dominant language and in some studies also when compared to corresponding monolinguals. In ERPs, language processing differences between bilinguals vs. monolinguals have typically been found in the N400 component. In the present study, highly proficient Finnish-Swedish bilinguals who had acquired both languages during childhood were compared to Finnish monolinguals during a visual lexical decision task and simultaneous ERP recordings. Behaviorally, we found that the response latencies were overall longer in bilinguals than monolinguals, and that the effects for all three factors, frequency, morphology, and lexicality were also larger in bilinguals even though they had acquired both languages early and were highly proficient in them. In line with this, the N400 effects induced by frequency, morphology, and lexicality were larger for bilinguals than monolinguals. Furthermore, the ERP results also suggest that while most inflected Finnish words are decomposed into stem and suffix, only monolinguals have encountered high frequency inflected word forms often enough to develop full-form representations for them. Larger behavioral and neural effects in bilinguals in these factors likely reflect lower amount of exposure to words compared to monolinguals, as the language input of bilinguals is divided between two languages.

Hemispheric asymmetries and cognitive flexibility: an ERP and sLORETA study

Although functional cerebral asymmetries (FCAs) affect all cognitive domains, their modulation of the efficacy of specific executive functions is largely unexplored. In the present study, we used a lateralized version of the task switching paradigm to investigate the relevance of hemispheric asymmetries for cognitive control processes. Words were tachistoscopically presented in the left (LVF) and right visual half field (RVF). Participants had to categorise the words either based on their initial letters, or according to their word type. On half of the trials the task changed (switch trials) whereas on the other half it stayed the same (repeat trials). ERPs were recorded and the neural sources of the ERPs were reconstructed using standardised low resolution brain electromagnetic tomography (sLORETA). In the word type task, participants were faster on repeat trials when stimuli were presented in the RVF. In contrast, in the initial letter task participants were faster on repeat trials and in general more accurate after stimulus presentation in the LVF. In both tasks, no hemispheric asymmetries in reaction times were observed on switch trials. On the electrophysiological level, we observed a left lateralization of the N1 that was mediated by activation in the left extrastriate cortex as well as a greater positivity of the P3b after stimulus presentation in the RVF compared to the LVF that was mediated by activation in the superior parietal cortex. These results show that FCAs affect the neurophysiological correlates of executive functions related to task switching. The relation of neurophysiological and behavioural asymmetries is mediated by task complexity, with more complex tasks leading to more interhemispheric interaction and smaller left-right differences in behavioural measures. These findings reveal that FCAs are an important modulator of executive functions related to cognitive flexibility.

Conflict Resolution in Sentence Processing by Bilinguals

The present study pursues findings from earlier behavioral research with children showing the superior ability of bilinguals to make grammaticality judgments in the context of misleading semantic information. The advantage in this task was attributed to the greater executive control of bilinguals, but this impact on linguistic processing has not been demonstrated in adults. Here, we recorded event-related potentials in young adults who were either English monolinguals or bilinguals as they performed two different language judgment tasks. In the acceptability task, participants indicated whether or not the sentence contained an error in either grammar or meaning; in the grammaticality task, participants indicated only whether the sentence contained an error in grammar, in spite of possible conflicting information from meaning. In both groups, sentence violations generated N400 and P600 waves. In the acceptability task, bilinguals were less accurate than monolinguals, but in the grammaticality task which requires more executive control, bilingual and monolingual groups showed a comparable level of accuracy. Importantly, bilinguals generated smaller P600 amplitude and a more bilateral distribution of activation than monolinguals in the grammaticality task requiring more executive control. Our results show that bilinguals use their enhanced executive control for linguistic processing involving conflict in spite of no apparent advantage in linguistic processing under simpler conditions.

Involuntary switching of attention mediates differences in event-related responses to complex tones between early and late Spanish-English bilinguals

Most research with bilinguals has used speech stimuli to demonstrate differences in auditory processing abilities. Two main factors have been identified as modulators of such differences: proficiency and age of acquisition of the second language (L2). However, whether the bilingual brain differs from the monolingual in the efficient processing of non-verbal auditory events (known to be critical to the acoustic analysis of the speech stream) remains unclear. In this EEG/ERP study, using the mismatch negativity (MMN), P3a, and late negativity (LN), we examined differences in discrimination, involuntary switching of attention and reorienting of attention between monolinguals and bilinguals as they processed complex tones. Further, we examined the role that age of acquisition plays in modulating such responses. A group of English monolinguals and a group of proficient Spanish-English bilinguals were presented with a multiple-deviant oddball paradigm with four deviant conditions (duration, frequency, silent gap, and frequency modulation). Late bilinguals, who learned English after age 10, exhibited larger MMN and P3a responses than early bilinguals, across all deviant conditions. Significant associations were found between amplitude of the responses and both age of L2 acquisition and years of L2 experience. Individuals who acquired English at later ages and had fewer years of L2 experience had larger MMN, P3a, and LN responses than those who learned it earlier. These findings demonstrate that age of L2 acquisition is an important modulator of auditory responses in bilinguals even when processing non-speech signals. Involuntary attention switching is suggested as the main factor driving these differences.

Spatiotemporal dynamics of bilingual word processing

Studies with monolingual adults have identified successive stages occurring in different brain regions for processing single written words. We combined magnetoencephalography and magnetic resonance imaging to compare these stages between the first (L1) and second (L2) languages in bilingual adults. L1 words in a size judgment task evoked a typical left-lateralized sequence of activity first in ventral occipitotemporal cortex (VOT: previously associated with visual word-form encoding) and then ventral frontotemporal regions (associated with lexico-semantic processing). Compared to L1, words in L2 activated right VOT more strongly from approximately 135 ms; this activation was attenuated when words became highly familiar with repetition. At approximately 400 ms, L2 responses were generally later than L1, more bilateral, and included the same lateral occipitotemporal areas as were activated by pictures. We propose that acquiring a language involves the recruitment of right hemisphere and posterior visual areas that are not necessary once fluency is achieved.

Left-lateralized N170 effects of visual expertise in reading: evidence from Japanese syllabic and logographic scripts

The N170 component of the event-related potential (ERP) reflects experience-dependent neural changes in several forms of visual expertise, including expertise for visual words. Readers skilled in writing systems that link characters to phonemes (i.e., alphabetic writing) typically produce a left-lateralized N170 to visual word forms. This study examined the N170 in three Japanese scripts that link characters to larger phonological units. Participants were monolingual English speakers (EL1) and native Japanese speakers (JL1) who were also proficient in English. ERPs were collected using a 129-channel array, as participants performed a series of experiments viewing words or novel control stimuli in a repetition detection task. The N170 was strongly left-lateralized for all three Japanese scripts (including logographic Kanji characters) in JL1 participants, but bilateral in EL1 participants viewing these same stimuli. This demonstrates that left-lateralization of the N170 is dependent on specific reading expertise and is not limited to alphabetic scripts. Additional contrasts within the moraic Katakana script revealed equivalent N170 responses in JL1 speakers for familiar Katakana words and for Kanji words transcribed into novel Katakana words, suggesting that the N170 expertise effect is driven by script familiarity rather than familiarity with particular visual word forms. Finally, for English words and novel symbol string stimuli, both EL1 and JL1 subjects produced equivalent responses for the novel symbols, and more left-lateralized N170 responses for the English words, indicating that such effects are not limited to the first language. Taken together, these cross-linguistic results suggest that similar neural processes underlie visual expertise for print in very different writing systems.

Orthographic familiarity, phonological legality and number of orthographic neighbours affect the onset of ERP lexical effects

Background

It has been suggested that the variability among studies in the onset of lexical effects may be due to a series of methodological differences. In this study we investigated the role of orthographic familiarity, phonological legality and number of orthographic neighbours of words in determining the onset of word/non-word discriminative responses.

Methods

ERPs were recorded from 128 sites in 16 Italian University students engaged in a lexical decision task. Stimuli were 100 words, 100 quasi-words (obtained by the replacement of a single letter), 100 pseudo-words (non-derived) and 100 illegal letter strings. All stimuli were balanced for length; words and quasi-words were also balanced for frequency of use, domain of semantic category and imageability. SwLORETA source reconstruction was performed on ERP difference waves of interest.

Results

Overall, the data provided evidence that the latency of lexical effects (word/non-word discrimination) varied as a function of the number of a word's orthographic neighbours, being shorter to non-derived than to derived pseudo-words. This suggests some caveats about the use in lexical decision paradigms of quasi-words obtained by transposing or replacing only 1 or 2 letters. Our findings also showed that the left-occipito/temporal area, reflecting the activity of the left fusiform gyrus (BA37) of the temporal lobe, was affected by the visual familiarity of words, thus explaining its lexical sensitivity (word vs. non-word discrimination). The temporo-parietal area was markedly sensitive to phonological legality exhibiting a clear-cut discriminative response between illegal and legal strings as early as 250 ms of latency.

Conclusion

The onset of lexical effects in a lexical decision paradigm depends on a series of factors, including orthographic familiarity, degree of global lexical activity, and phonologic legality of non-words.

Language selection in bilingual speech: evidence for inhibitory processes

Although bilinguals rarely make random errors of language when they speak, research on spoken production provides compelling evidence to suggest that both languages are active when only one language is spoken (e.g., [Poulisse, N. (1999). Slips of the tongue: Speech errors in first and second language production. Amsterdam/Philadelphia: John Benjamins]). Moreover, the parallel activation of the two languages appears to characterize the planning of speech for highly proficient bilinguals as well as second language learners. In this paper, we first review the evidence for cross-language activity during single word production and then consider the two major alternative models of how the intended language is eventually selected. According to language-specific selection models, both languages may be active but bilinguals develop the ability to selectively attend to candidates in the intended language. The alternative model, that candidates from both languages compete for selection, requires that cross-language activity be modulated to allow selection to occur. On the latter view, the selection mechanism may require that candidates in the nontarget language be inhibited. We consider the evidence for such an inhibitory mechanism in a series of recent behavioral and neuroimaging studies.

Bilingual and monolingual brains compared: a functional magnetic resonance imaging investigation of syntactic processing and a possible "neural signature" of bilingualism

Abstract Does the brain of a bilingual process language differently from that of a monolingual? We compared how bilinguals and monolinguals recruit classic language brain areas in response to a language task and asked whether there is a "neural signature" of bilingualism. Highly proficient and early-exposed adult Spanish-English bilinguals and English monolinguals participated. During functional magnetic resonance imaging (fMRI), participants completed a syntactic "sentence judgment task" [Caplan, D., Alpert, N., & Waters, G. Effects of syntactic structure and propositional number on patterns of regional cerebral blood flow. Journal of Cognitive Neuroscience, 10, 541-552, 1998]. The sentences exploited differences between Spanish and English linguistic properties, allowing us to explore similarities and differences in behavioral and neural responses between bilinguals and monolinguals, and between a bilingual's two languages. If bilinguals' neural processing differs across their two languages, then differential behavioral and neural patterns should be observed in Spanish and English. Results show that behaviorally, in English, bilinguals and monolinguals had the same speed and accuracy, yet, as predicted from the Spanish-English structural differences, bilinguals had a different pattern of performance in Spanish. fMRI analyses revealed that both monolinguals (in one language) and bilinguals (in each language) showed predicted increases in activation in classic language areas (e.g., left inferior frontal cortex, LIFC), with any neural differences between the bilingual's two languages being principled and predictable based on the morphosyntactic differences between Spanish and English. However, an important difference was that bilinguals had a significantly greater increase in the blood oxygenation level-dependent signal in the LIFC (BA 45) when processing English than the English monolinguals. The results provide insight into the decades-old question about the degree of separation of bilinguals' dual-language representation. The differential activation for bilinguals and monolinguals opens the question as to whether there may possibly be a "neural signature" of bilingualism. Differential activation may further provide a fascinating window into the language processing potential not recruited in monolingual brains and reveal the biological extent of the neural architecture underlying all human language.

Shining new light on the brain's "bilingual signature": a functional Near Infrared Spectroscopy investigation of semantic processing

Decades of research have shown that, from an early age, proficient bilinguals can speak each of their two languages separately (similar to monolinguals) or rapidly switch between them (dissimilar to monolinguals). Thus we ask, do monolingual and bilingual brains process language similarly or dissimilarly, and is this affected by the language context? Using an innovative brain imaging technology, functional Near Infrared Spectroscopy (fNIRS), we investigated how adult bilinguals process semantic information, both in speech and in print, in a monolingual language context (one language at a time) or in a bilingual language context (two languages in rapid alternation). While undergoing fNIRS recording, ten early exposed, highly proficient Spanish-English bilinguals completed a Semantic Judgment task in monolingual and bilingual contexts and were compared to ten English monolingual controls. Two hypotheses were tested: the Signature Hypothesis predicts that early, highly proficient bilinguals will recruit neural tissue to process language differently from monolinguals across all language contexts. The Switching Hypothesis predicts that bilinguals will recruit neural tissue to process language similarly to monolinguals, when using one language at a time. Supporting the Signature Hypothesis, in the monolingual context, bilinguals and monolinguals showed differences in both hemispheres in the recruitment of DLPFC (BA 46/9) and IFC (BA 47/11), but similar recruitment of Broca's area (BA 44/45). In particular, in the monolingual context, bilinguals showed greater signal intensity in channels maximally overlaying DLPFC and IFC regions as compared to monolinguals. In the bilingual context, bilinguals demonstrated a more robust recruitment of right DLPFC and right IFC. These findings reveal how extensive early bilingual exposure modifies language organization in the brain-thus imparting a possible "bilingual signature." They further shed fascinating new light on how the bilingual brain may reveal the biological extent of the neural architecture underlying all human language and the language processing potential not fully recruited in the monolingual brain.

ERP evidence for different strategies in the processing of case markers in native speakers and non-native learners

Background

The present experiments were designed to test how the linguistic feature of case is processed in Japanese by native and non-native listeners. We used a miniature version of Japanese as a model to compare sentence comprehension mechanisms in native speakers and non-native learners who had received training until they had mastered the system. In the first experiment we auditorily presented native Japanese speakers with sentences containing incorrect double nominatives and incorrect double accusatives, and with correct sentences. In the second experiment we tested trained non-natives with the same material. Based on previous research in German we expected an N400-P600 biphasic ERP response with specific modulations depending on the violated case and whether the listeners were native or non-native.

Results

For native Japanese participants the general ERP response to the case violations was an N400-P600 pattern. Double accusatives led to an additional enhancement of the P600 amplitude. For the learners a native-like P600 was present for double accusatives and for double nominatives. The additional negativity, however, was present in learners only for double nominative violations, and it was characterized by a different topographical distribution.

Conclusion

The results indicate that native listeners use case markers for thematic as well as syntactic structure building during incremental sentence interpretation. The modulation of the P600 component for double accusatives possibly reflects case specific syntactic restrictions in Japanese. For adult language learners later processes, as reflected in the P600, seem to be more native-like compared to earlier processes. The anterior distribution of the negativity and its selective emergence for canonical sentences were taken to suggest that the non-native learners resorted to a rather formal processing strategy whereby they relied to a large degree on the phonologically salient nominative case marker.

ERP measures of auditory word repetition and translation priming in bilinguals

Motivated by the demonstration of similarly localized adaptation of the hemodynamic response in a first (L1) and second (L2) language, this study examined event-related brain potentials (ERPs) to spoken words in L1 and L2 in 15 English-French bilinguals. We examined whether the temporal pattern of N400 adaptation due to within-language repetitions (i.e., repetition priming) was similar in L1 and L2 and whether the release from adaptation elicited by a within-language word change was similar. Furthermore, using word changes across language, we examined the phonological mismatch negativity (PMN) and N400 components to determine the kind of information activated during translation priming. In contrast to within-language repetition, we expected between-language repetition (i.e., translations) to be characterized by conceptual rather than lexical/phonological word form priming. Overall, the pattern of adaptation and release from adaptation was similar in L1 and L2, with evidence of delayed semantic analysis in L2 in the form of a later N400 effect. A change in language (L1 to L2) elicited a similar pattern of PMN and N400 activity compared to a within-language change in meaning in L1, suggesting that neither word form nor conceptual information was available on-line for the forward translation. In contrast, the presence of strong PMN but minimal N400 effects for L2-to-L1 translations suggests that conceptual but not phonological information is available on-line for backwards translation. L2 proficiency influenced the extent to which conceptual representations were activated by translations. These data are discussed in light of current models of bilingual word processing and suggest modality differences in the pattern of activation of lexical and conceptual information.

Orthographic transparency and grapheme–phoneme conversion: An ERP study in Arabic and French readers

Numerous behavioral studies have suggested that orthographic transparency of a language is liable to influence the use of grapheme-phoneme conversion during reading. In order to test this hypothesis, the effect of orthographic transparency on event-related potentials was assessed by comparing French to Arab readers. Indeed, French language, contrary to Arabic one, was expected to favor the use of grapheme-phoneme rules during reading. Our results demonstrated that the N320, a component implicated in phonologic transcription, was modulated by orthographic transparency. Indeed, during reading in their mother tongue, only French subjects clearly elicited a N320. Moreover, the comparisons between activations elicited by Arabic words in Arab subjects and French monolingual people also confirm that the N170 component represents an important orthographic stage. The implications of these results on bilinguism and visual word recognition models are discussed.

Perceptual and lexical effects in letter identification: An event-related potential study of the word superiority effect

Most classical models of visual word recognition are based on sequentially organized levels of representation and involve feedback mechanisms to various extents. In this study, we aim at clarifying which of the early processing stages of visual word recognition are modulated by top-down lexical effects. We studied the identification of letters embedded in briefly presented words (e.g., TABLE) and illegal nonwords (e.g., GTFRS) using event-related potentials (ERPs). Participants were involved in the Reicher-Wheeler paradigm: they were asked to indicate which of two letters displayed above and below a string of hashes was flashed immediately before at fixation within a letter string, which was either a word or a nonword. Event-related potentials were significantly modulated by the lexical status of stimuli around 200 ms after stimulus onset, i.e., in the peaking window of the N1 component. In light of our results, we propose that visual word form representations can constrain letter identification at a prelexical stage i.e., during the extraction of letter-shape information. In addition, we show that this facilitatory top-down effect is sensitive to stimulus exposure duration.

Processing of conceptual relationships within simple Czech and English sentences--ERPs and behavioral correlates

The paper presents findings of an experiment the participants of which were native Czech speakers (L1 ) possessed of perfect knowledge of English (L2). We assumed that the subjects could process differently each of the three types of English and Czech sentences; the first type represented correct sentences, the other two violated sentences. Violated sentences differed in the precise relationship between the verbs, their preceding noun phrases, and their preceding context. ERPs to critical verbs, the accuracy rate for both English and Czech sentences processing and decision time for each were evaluated. Participants' personality traits were assessed too. It has been shown that our subjects, who learned English after the age of 15, displayed significant differences in all measured parameters. It was especially the longer latency N400, the lower accuracy rate of English sentence processing, the longer decision time, and the same dynamics of all measured ERPs parameters. Possible causes of these differences are discussed.

Bilingual brain organization: A functional magnetic resonance adaptation study

We used functional magnetic resonance adaptation (fMRA) to examine whether intra-voxel functional specificity may be present for first (L1)- and second (L2)-language processing. We examined within- and across-language adaptation for spoken words in English-French bilinguals who had acquired their L2 after the age of 4 years. Subjects listened to words presented binaurally through earphones. In two control conditions (one for each language), six identical words were presented to obtain maximal adaptation. The remaining six conditions each consisted of five words that were identical followed by a sixth word that differed. There were thus a total of eight experimental conditions: no-change (sixth word identical to first five); a change in meaning (different final word in L1); a change in language (final item translated into L2); a change in meaning and language (different final word in L2). The same four conditions were presented in L2. The study also included a silent baseline. At the neural level, within- and across-language word changes resulted in release from adaptation. This was true for separate analyses of L1 and L2. We saw no evidence for greater recovery from adaptation in across-language relative to within-language conditions. While many brain regions were common to L1 and L2, we did observe differences in adaptation for forward translation (L1 to L2) as compared to backward translation (L2 to L1). The results support the idea that, at the lexical level, the neural substrates for L1 and L2 in bilinguals are shared, but with some populations of neurons within these shared regions showing language-specific responses.

Testing a model for bilingual semantic priming with interlingual homographs: RT and N400 effects

Using a semantic priming paradigm, this study examines the effects of semantic and lexical-orthographic context on reaction times (RTs) and event-related potentials (ERPs) for interlingual homographs. Dutch-English bilinguals performed an English lexical decision task in which homographs like STEM (meaning "voice" in Dutch) were preceded by primes like ROOT or FOOL that were semantically related or unrelated to the English reading of the target word. Homographs were responded to faster following semantically related primes than following unrelated primes. The responses in both conditions were modulated by the relative frequencies of the two readings of the homographs: responses were faster when their English word frequency was high or when their Dutch word frequency was low. In the ERPs, N400 effects, taken to reflect processes of semantic integration, were found for homographs preceded by related primes. Remarkably, the amplitude of the N400 effect was also modulated by word frequency in both the first (Dutch, L1) and the second (English, L2) language. The observed relationship between lexical and semantic variables supports a model for bilingual semantic priming that extends the language nonselective BIA+ model for bilingual word recognition.

Processing semantic anomalies in two languages: an electrophysiological exploration in both languages of Spanish–English bilinguals

The latency of the brain response to semantic anomalies (N400 effect) has been found to be longer in a bilingual's second language (L2) than in their first language (L1) and/or to that seen in monolinguals. This has been explained in terms of late exposure to L2, although age of exposure and language proficiency are often highly correlated. We thus examined the relative contributions of these factors not only in L2 but also in L1 in a group of Spanish-English bilinguals for whom age of exposure and language proficiency were not highly correlated by recording event-related brain potentials (ERPs) to semantically congruous/incongruous words completing written sentences. We also divided our bilinguals into a Spanish-dominant subset who had late exposure and reduced vocabulary proficiency [as measured by Boston Naming Test (BNT) and Verbal Fluency Scores] in L2 (English) relative to L1 (Spanish) and an English-dominant group who had early exposure to both their languages although greater proficiency in English than in Spanish. In both groups, the N400 effect was significantly later in the nondominant than the dominant language. Although this slowing could be due to late exposure to English in the Spanish-dominant group, late exposure cannot explain the slowing in Spanish in the English-dominant group. Overall, we found that vocabulary proficiency and age of exposure are both important in determining the timing of semantic integration effects during written sentence processing--with vocabulary proficiency predicting the timing of semantic analysis in L1 and both age of exposure and language proficiency, although highly correlated, making additional small but uncorrelated contributions to the speed of semantic analysis/integration in L2.