ERP priming studies of bilingual language processing

The aim of this review is to provide a selective overview of priming studies which have employed the event-related brain potential (ERP) technique in order to investigate bilingual language processing. The priming technique can reveal an implicit memory effect in which exposure to one stimulus influences the processing of another stimulus. Behavioral approaches, such as measuring reaction times, may not always be enough for providing a full view on the exact mechanisms and the time-course of language comprehension. Instead, ERPs have a time-resolution of a millisecond and hence they offer a precise temporal overview of the underlying neural processes involved in language processing. In our review, we summarize experimental research that has combined priming with ERP measurements, thus creating a valuable tool for examining the neurophysiological correlates of language processing in the bilingual brain.Peer reviewe

Neurocognitive processing of inflected and derived words

The representation of morphologically complex words in the mental lexicon and their neurocognitive processing has been a vigorously debated topic in psycholinguistics and the cognitive neuroscience of language. This thesis investigates the effect of stimulus modality on morphological processing, the spatiotemporal dynamics of the neural processing of inflected (e.g., work+ed ) and derived (e.g., work+er ) words and their interaction, using the Finnish language. Overall, the results suggest that the constituent morphemes of isolated written and spoken inflected words are accessed separately, whereas spoken derived words activate both their full form and the constituent morphemes. The processing of both spoken and written inflected words elicited larger N400 responses than monomorphemic words (Study I), whereas the responses to spoken derived words did not differ from those to monomorphemic words (Study IV). Spoken inflected words elicited a larger left-lateralized negativity and greater source strengths in the left temporal cortices than derived words (Study IV). Thus, the results suggest different cortical processing for derived and inflected words. Moreover, the neural mechanisms underlying inflection and derivation seem to be not only different, but also independent as indexed by the linear summation of the responses to derived and inflected stimuli in a combined (derivation+inflection) condition (Study III). Furthermore, the processing of meaningless, spoken derived pseudowords was more difficult than for existing derived words, indexed by a larger N400-type effect for the pseudowords. However, no differences were observed between meaningful derived pseudowords and existing derived words (Study II). The results of Study II suggest that semantic compatibility between morphemes seems to have a crucial role in a successful morphological analysis. As a methodological note, time-locking the auditory event-related potentials/fields (ERP/ERF) to the suffix onset revealed the processes related to morphological analysis more precisely (Studies II and IV), which also enables comparison of the neural processes in different modalities (Study I).Morfologisesti kompleksisten, eli useammasta itsenäisestä merkitysyksiköstä muodostuvien sanojen käsittely aivoissa on ollut vilkkaan keskustelun kohteena psykolingvistiikassa sekä kielen kognitiivisessa neurotieteessä. Tällaisia morfologisesti kompleksisia sanoja ovat esimerkiksi taivutetut ( työ + tä ) ja johdetut ( työ + tön ) sanat. Erityisesti keskustelua on käyty siitä, missä määrin tällaiset sanat haetaan muistista kokonaisina ja mikä tehtävä on mekanismilla, joka pilkkoo päätteet (kuten tä ja tön ) sanavartaloista. Samoin on ollut vielä epäselvyyttä siitä miten kuullun ja luetun kielen käsittelymekanismit eroavat toisistaan. Tässä väitöskirjassa tutkittiin taivutettujen ja johdettujen sanojen hermostollista käsittelyä, niiden välistä vuorovaikutusta sekä aistipiirin vaikutusta sanojen morfologian käsittelyyn. Väitöskirjatutkimuksen perusteella on mahdollista olettaa, että taivutettujen sanojen morfeemit ( työ + tä ) käsitellään erikseen lukemisen tai sanan kuulemisen aikana, kun taas johdosten osalta aktivoituvat sekä koko sanan edustuma ( työtön ) että yksittäiset morfeemit ( työ + tön ). Taivutuspäätteen yhdistäminen sanavartaloon aktivoi voimakkaammin vasemman aivopuoliskon LAN- ja N400-vasteita. MEG-kokeessa löydettiin erityisesti taivutukseen liittyvä hermostollinen vaste ohimolohkon alueella. Tulosten mukaan taivutuksen ja johtamisen hermostolliset taustamekanismit ovat toisistaan erillisiä ja lisäksi myös ainakin osittain toisistaan riippumattomia. Jälkimmäistä havaintoa tuki tulos, jonka mukaan yhdistelmätilanteen aiheuttamat jännitevasteet olivat selitettävissä johtamisen ja taivutuksen erikseen aiheuttamien jännitevasteiden yhtäaikaisella summautumisella. Morfologisesti kompleksisten sanojen lukemisen ja kuulemisen mekanismien välillä havaittiin myös eroja. Tämä johtunee siitä, että kuultaessa sanaa käsitellään koko ajan sen edetessä ajassa, kun visuaalisessa modaliteetissa puolestaan kielellinen informaatio tullee käyttöön kokonaisena nopeammin. Tästä johtuen morfologisia prosesseja tutkittaessa pitää kiinnittää erityistä huomiota siihen, millä ajanhetkellä morfologinen informaatio on aivojen käytettävissä aistipiiristä riippuen. Väitöskirjatyössä kehitetty suffiksilukittujen vasteiden menetelmä auttaa tässä vertailussa

Neural mechanisms underlying word- and phrase-level morphological parsing

How is morphological and morphosyntactic information processed during sentence reading? Are the neural mechanisms underlying word- and phrase-level combinatorial processing overlapping or distinct? Here, electroencephalography (EEG) and magnetoencephalography (MEG) responses were recorded simultaneously during silent reading of Finnish sentences. The experimental conditions included 1) well-formed grammatical sentences (correct condition), 2) sentences containing morphosyntactic violations (adjective–noun number agreement violations), 3) morphological violations (incorrect stem allomorph and inflectional suffix combination), and 4) combined violations, containing both morphosyntactic and morphological violations. Signal space and source modeling results showed that morphosyntactic violations elicited a left anterior negativity effect, generated particularly in the left inferior frontal area. Morphological violations elicited a widespread negativity, resembling the N400. The neural sources of this negativity were localized most prominently to the right temporal cortical networks. Furthermore, all violations elicited P600 effects with similar widespread bilateral fronto-temporal neural generators that did not differ between morphosyntactic and morphological conditions. Our findings suggest at least partially distinct subnetworks in the fronto-temporal cortices for morphological and morphosyntactic parsing during the earlier stages of processes (∼400 ms post stimulus onset) and shared neural generators for the later processing stages.Peer reviewe

Shaving bridges and tuning kitaraa : the effect of language switching on semantic processing

Language switching has been repeatedly found to be costly. Yet, there are reasons to believe that switches in language might benefit language comprehension in some groups of people, such as less proficient language learners. This study therefore investigated the interplay between language switching and semantic processing in groups with varying language proficiency. EEG was recorded while L2 learners of English with intermediate and high proficiency levels read semantically congruent or incongruent sentences in L2. Translations of congruent and incongruent target words were additionally presented in L1 to create intrasentential language switches. A control group of English native speakers was tested in order to compare responses to non-switched stimuli with those of L2 learners. An omnibus ANOVA including all groups revealed larger N400 responses for non-switched incongruent stimuli compared to congruent stimuli. Additionally, despite switches to L1 at target word position, semantic N400 responses were still elicited in both L2 learner groups. Further switching effects were reflected by an N400-like effect and a late positivity complex (LPC), pointing to possible parsing efforts after language switches. Our results therefore show that although language switches are associated with increased mental effort, switches may not necessarily be costly on the semantic level. This finding contributes to the ongoing discussion on language inhibition processes, and shows that, in these intermediate and high proficiency English L2 learners, semantic processes look similar to those of native speakers of English.Peer reviewe

Auditory evoked potentials to speech and nonspeech stimuli are associated with verbal skills in preschoolers

Children's obligatory auditory event-related potentials (ERPs) to speech and nonspeech sounds have been shown to associate with reading performance in children at risk or with dyslexia and their controls. However, very little is known of the cognitive processes these responses reflect. To investigate this question, we recorded ERPs to semisynthetic syllables and their acoustically matched nonspeech counterparts in 63 typically developed preschoolers, and assessed their verbal skills with an extensive set of neurocognitive tests. P1 and N2 amplitudes were larger for nonspeech than speech stimuli, whereas the opposite was true for N4. Furthermore, left-lateralized P1s were associated with better phonological and prereading skills, and larger P1s to nonspeech than speech stimuli with poorer verbal reasoning performance. Moreover, left-lateralized N2s, and equal-sized N4s to both speech and nonspeech stimuli were associated with slower naming. In contrast, children with equal-sized N2 amplitudes at left and right scalp locations, and larger N4s for speech than nonspeech stimuli, performed fastest. We discuss the possibility that children’s ERPs reflect not only neural encoding of sounds, but also sound quality processing, memory-trace construction, and lexical access. The results also corroborate previous findings that speech and nonspeech sounds are processed by at least partially distinct neural substrates.Peer reviewe

Effect of language experience on selective auditory attention: An event-related potential study

Dual language experience has typically been shown to improve various executive control functions. We investigated with event-related brain potentials (ERPs) recorded from early (natively) bilingual speakers and control participants whether it also affects auditory selective attention. We delivered to our participants two tone streams, one to the left and one to the right ear. Both streams consisted of standard tones and two types of infrequent deviant tones which had either an enhanced duration or intensity. The participants were instructed to attend either to the right or left stream and to detect longer-duration deviants in the attended stream. The results showed that the early bilinguals did not outperform the controls in target detection accuracy or speed. However, the late portion of the attention-related ERP modulation (the negative difference, Nd) was larger over the left hemisphere in the early bilinguals than in the controls, suggesting that the maintenance of selective attention or further processing of selectively attended sounds is enhanced in the bilinguals. Moreover, the late reorienting negativity (RON) in response to intensity-deviant tones was larger in the bilinguals, suggesting more efficient disengagement of attention from distracting auditory events. Hence, our results demonstrate that brain responses associated with certain aspects of auditory attention are enhanced in the bilingual adults, indicating that early dual language exposure modulates the neuronal responsiveness of auditory modality.Peer reviewe

Acquisition of L2 morphology by adult language learners

Learning a new language requires the acquisition of morphological units that enable the fluent use of words in different grammatical contexts. While accumulating research has elucidated the neural processing of native morphology, much less is known about how second-language (L2) learners acquire and process morphology in their L2. To address this question, we presented native speakers as well as beginning and advanced learners of Finnish with spoken (1) derived words, (2) inflected words, (3) novel derivations (novel combinations of existing stem + suffix), and (4) pseudo-suffixed words (existing stem + pseudo-suffix) in a passive listening EEG experiment. An early (60 msec after suffix deviation point) positive ERP response showed no difference between inflections and derivations, suggesting similar early parsing of these complex words. At 130 msec, derivations elicited a lexical ERP pattern of full-form memory-trace activation, present in the L2 beginners and advanced speakers to different degrees, implying a shift from lexical processing to more dual parsing and lexical activation of the complex forms with increasing proficiency. Pseudo-suffixed words produced a syntactic pattern in a later, 170 240 msec time-window, exhibiting enhanced ERPs compared to well-formed inflections, indicating second-pass syntactic parsing. Overall, the L2 learners demonstrated a gradual effect of proficiency towards L1-like responses. Advanced L2 learners seem to have developed memory traces for derivations and their neurolinguistic system is capable of early automatic parsing. This suggests that advanced learners have already developed sensitivity to morphological information, while such knowledge is weak in beginners. Discrepancies in ERP dynamics and topographies indicate partially differing recruitment of the language network in L1 and L2. In beginners, response differences between existing and novel morphology were scarce, implying that representations for complex forms are not yet well-established. The results suggest successful development of brain mechanisms for automatic processing of L2 morphology, capable of gradually attaining L1-like functionality with increasing proficiency. (C) 2019 The Authors. Published by Elsevier Ltd.Peer reviewe

Editorial : Neurobehavioral changes in language learning

Peer reviewe

Quick reorganization of memory traces for morphologically complex words in young children

Formation of neural mechanisms for morphosyntactic processing in young children is still poorly understood. Here, we addressed neural processing and rapid online acquisition of familiar and unfamiliar combinations of morphemes. Three different types of morphologically complex words - derived, inflected, and novel (pseudostem + real suffix) - were presented in a passive listening setting to 16 typically developing 3-4-year old children (as part of a longitudinal Helsinki SLI follow-up study). The mismatch negativity (MMN) component of event-related potentials (ERP), an established index of long-term linguistic memory traces in the brain, was analysed separately for the initial and final periods of the exposure to these items. We found MMN response enhancement for the inflected words towards the end of the recording session, whereas no response change was observed for the derived or novel complex forms. This enhancement indicates rapid build-up of a new memory trace for the combination of real morphemes, suggesting a capacity for online formation of whole-form lexicalized representations as one of the morphological mechanisms in the developing brain. Furthermore, this enhancement increased with age, suggesting the development of automatic morphological processing circuits in the age range of 3-4 years.Peer reviewe

Semantic training facilitates the acquisition of novel morphemes : MEG evidence

Learning to recognize morphemic boundaries is essential for fluent language use. In languages with rich morphology, the question of morphological learning is particularly relevant. Some neurocognitive models propose that morphologically complex words are parsed and their constituents are stored as separate units in lexical memory. Neural mechanisms underlying the acquisition of such novel morphological units, however, remain largely unexplored. Here, we trained 19 native Finnish-speaking participants with novel derivational suffixes through a word-picture association task. Following this short training session, we used magnetoencephalography to record the participants’ brain responses to trained and untrained suffixes combined with new real and pseudoword stems in a 22-minute passive listening task. Existing Finnish suffixes served as controls. We compared the responses measured early and late (first/last 5 minutes) during passive exposure to investigate the online build-up of novel suffix representations. In the left frontal and temporal cortices, source activation for real suffixes was significantly higher than for both trained and untrained novel suffixes in the 60-80 ms, 120-140 ms and 220-260 ms time-windows (around ERF peaks) following the suffix onset, suggesting the activation of pre-existing long-term memory traces. However, we also found increased source amplitudes for the trained as opposed to the untrained suffixes already early in exposure. Although such a brief exposure may not be sufficient for the integration of novel morphological units into lexical memory, our findings suggest that a short semantic training of novel affixes facilitates morphological decomposition and speeds up suffix memory trace formation in the left fronto-temporal language networks.Peer reviewe