Individual language experience modulates rapid formation of cortical memory circuits for novel words

Speech comprehension across time, space, frequency, and age: MEG-MVPA classification of intertrial phase coherence

Language is a key part of human cognition, essential for our well-being at all stages of our lives. Whereas many neurocognitive abilities decline with age, for language the picture is much less clear, and how exactly speech comprehension changes with ageing is still unknown. To investigate this, we employed magnetoencephalography (MEG) and recorded neuromagnetic brain responses to auditory linguistic stimuli in healthy participants of younger and older age using a passive task-free paradigm and a range of different linguistic stimulus contrasts, which enabled us to assess neural processing of spoken language at multiple levels (lexical, semantic, morphosyntactic). Using machine learning-based classification algorithms to scrutinise intertrial phase coherence of MEG responses in cortical source space, we found that patterns of oscillatory neural activity diverged between younger and older participants across several frequency bands (alpha, beta, gamma) for all tested linguistic information types. The results suggest multiple age-related changes in the brain's neurolinguistic circuits, which may be due to both healthy ageing in general and compensatory processes in particular.

Understanding Language Attrition through Orthography

The decay in the proficiency of the native language (L1), known as first language attrition, is one of the least understood phenomena associated with the acquisition of a second language (L2). Indeed, the exact cause for the deterioration in L1 performance, be that either the interference from L2 acquisition or the less frequent use of L1, still remains elusive. In this opinion paper, we focus on one largely understudied aspect of L1 attrition—namely, the erosion of the L1 orthographic knowledge under the influence of L2 orthography. In particular, we propose to study differences in orthographic processing between mono- and bilingual populations as an approach, which, in turn, will allow to address both cognitive and neurophysiological mechanisms underlying L1 attrition. We discuss relevant experimental paradigms, variable manipulations and appropriate research methods that may help disentangle the largely debated question of L2 interference vs. L1 disuse, clarifying the nature of the L1 orthographic attrition.

Language and nonlanguage factors in foreign language learning: evidence for the learning condition hypothesis

The question of why native and foreign languages are learned with a large performance gap has prompted language researchers to hypothesize that they are subserved by fundamentally different mechanisms. However, this hypothesis may not have taken into account that these languages can be learned under different conditions (e.g., naturalistic vs. classroom settings). With a large sample of 636 third language (L3) learners who learned Chinese and English as their first (L1) and second (L2) languages, the present study examined the association of learning success across L1-L3. We argue that learning conditions may reveal how these languages are associated in terms of learning success. Because these languages were learned under a continuum of naturalistic to classroom conditions from L1 to L3, this sample afforded us a unique opportunity to evaluate the hypothesis that similar learning conditions between languages could be an important driving force determining language learning success. After controlling for nonlanguage factors such as musical background and motivational factors and using a convergence of analytics including the general linear models, the structural equation models, and machine learning, we found that the closer two languages were on the continuum of learning conditions, the stronger their association of learning success. Specifically, we found a significant association between L1 and L2 and between L2 and L3, but not between L1 and L3. Our results suggest that learning conditions may have important implications for the learning success of L1-L3.

Contextual Acquisition of Concrete and Abstract Words: Behavioural and Electrophysiological Evidence

Abstract and concrete words differ in their cognitive and neuronal underpinnings, but the exact mechanisms underlying these distinctions are unclear. We investigated differences between these two semantic types by analysing brain responses to newly learnt words with fully controlled psycholinguistic properties. Experimental participants learned 20 novel abstract and concrete words in the context of short stories. After the learning session, event-related potentials (ERPs) to newly learned items were recorded, and acquisition outcomes were assessed behaviourally in a range of lexical and semantic tasks. Behavioural results showed better performance on newly learnt abstract words in lexical tasks, whereas semantic assessments showed a tendency for higher accuracy for concrete words. ERPs to novel abstract and concrete concepts differed early on, ~150 ms after the word onset. Moreover, differences between novel words and control untrained pseudowords were observed earlier for concrete (~150 ms) than for abstract (~200 ms) words. Distributed source analysis indicated bilateral temporo-parietal activation underpinning newly established memory traces, suggesting a crucial role of Wernicke’s area and its right-hemispheric homologue in word acquisition. In sum, we report behavioural and neurophysiological processing differences between concrete and abstract words evident immediately after their controlled acquisition, confirming distinct neurocognitive mechanisms underpinning these types of semantics.

Electrophysiological Evidence of Dissociation Between Explicit Encoding and Fast Mapping of Novel Spoken Words

Existing behavioral, neuropsychological and functional neuroimaging data suggest that at least two major cognitive strategies are used for new word learning: fast mapping (FM) via context-dependent inference and explicit encoding (EE) via direct instruction. However, these distinctions remain debated at both behavioral and neurophysiological levels, not least due to confounds related to diverging experimental settings. Furthermore, the neural dynamics underpinning these two putative processes remain poorly understood. To tackle this, we designed a paradigm presenting 20 new spoken words in association with pictures in either FM or EE settings, closely matched for auditory and visual features and overall task demands. We tested word acquisition using a range of behavioral measures as well as passive event-related potential (ERP) responses, an established measure of word memory trace activation, and compared brain activity elicited by novel FM and EE words before and after the learning session. Behavioral data obtained in free recall, recognition and semantic word-picture matching tasks indicated successful acquisition of new words after just 10 exposures. Crucially, we found no behavioral evidence of different acquisition outcomes between FM and EE learning. ERP data, which exhibited the main response peaks at ~170, 250, and 520 ms, also indicated successful learning, with statistically different responses between novel and familiar words present only before, but not after the training, suggesting rapid formation of new neural memory circuits matching in activation those for previously known words. Furthermore, already at the earliest peak, we found different topographic distributions for the two learning types, with left-lateralized FM dynamics, suggestive of core language system involvement, and more diffuse activity for EE items, possibly suggesting the role of attention/executive control network. A similar effect also manifested later, at ~520 ms. Our data suggest that while both EE and FM learning can be successful for rapid word acquisition at the behavioral level, the diverging electrophysiological patterns suggest a dissociation between the neural systems underpinning these learning strategies.

Semantic Grounding of Novel Spoken Words in the Primary Visual Cortex

Embodied theories of grounded semantics postulate that, when word meaning is first acquired, a link is established between symbol (word form) and corresponding semantic information present in modality-specific—including primary—sensorimotor cortices of the brain. Direct experimental evidence documenting the emergence of such a link (i.e., showing that presentation of a previously unknown, meaningless word sound induces, after learning, category-specific reactivation of relevant primary sensory or motor brain areas), however, is still missing. Here, we present new neuroimaging results that provide such evidence. We taught participants aspects of the referential meaning of previously unknown, senseless novel spoken words (such as “Shruba” or “Flipe”) by associating them with either a familiar action or a familiar object. After training, we used functional magnetic resonance imaging to analyze the participants’ brain responses to the new speech items. We found that hearing the newly learnt object-related word sounds selectively triggered activity in the primary visual cortex, as well as secondary and higher visual areas.These results for the first time directly document the formation of a link between the novel, previously meaningless spoken items and corresponding semantic information in primary sensory areas in a category-specific manner, providing experimental support for perceptual accounts of word-meaning acquisition in the brain.

Rapid acquisition of novel written word-forms: ERP evidence

Background

Novel word acquisition is generally believed to be a rapid process, essential for ensuring a flexible and efficient communication system; at least in spoken language, learners are able to construct memory traces for new linguistic stimuli after just a few exposures. However, such rapid word learning has not been systematically found in visual domain, with different confounding factors obscuring the orthographic learning of novel words. This study explored the changes in human brain activity occurring online, during a brief training with novel written word-forms using a silent reading task

Results

Single-trial, cluster-based random permutation analysis revealed that training caused an extremely fast (after just one repetition) and stable facilitation in novel word processing, reflected in the modulation of P200 and N400 components, possibly indicating rapid dynamics at early and late stages of the lexical processing. Furthermore, neural source estimation of these effects revealed the recruitment of brain areas involved in orthographic and lexico-semantic processing, respectively.

Conclusions

These results suggest the formation of neural memory traces for novel written word-forms after a minimal exposure to them even in the absence of a semantic reference, resembling the rapid learning processes known to occur in spoken language.

Neurophysiological Correlates of Top-Down Phonological and Semantic Influence during the Orthographic Processing of Novel Visual Word-Forms

The acquisition of new vocabulary is usually mediated by previous experience with language. In the visual domain, the representation of orthographically unfamiliar words at the phonological or conceptual levels may facilitate their orthographic learning. The neural correlates of this advantage were investigated by recording EEG activity during reading novel and familiar words across three different experiments (n = 22 each), manipulating the availability of previous knowledge on the novel written words. A different pattern of event-related potential (ERP) responses was found depending on the previous training, resembling cross-level top-down interactive effects during vocabulary acquisition. Thus, whereas previous phonological experience caused a modulation at the post-lexical stages of the visual recognition of novel written words (~520 ms), additional semantic training influenced their processing at a lexico-semantic stage (~320 ms). Moreover, early lexical differences (~180 ms) elicited in the absence of previous training did not emerge after both phonological and semantic training, reflecting similar orthographic processing and word-form access.

Rapid Cortical Plasticity Induced by Active Associative Learning of Novel Words in Human Adults

Human speech requires that new words are routinely memorized, yet neurocognitive mechanisms of such acquisition of memory remain highly debatable. Major controversy concerns the question whether cortical plasticity related to word learning occurs in neocortical speech-related areas immediately after learning, or neocortical plasticity emerges only on the second day after a prolonged time required for consolidation after learning. The functional spatiotemporal pattern of cortical activity related to such learning also remains largely unknown. In order to address these questions, we examined magnetoencephalographic responses elicited in the cerebral cortex by passive presentations of eight novel pseudowords before and immediately after an operant conditioning task. This associative procedure forced participants to perform an active search for unique meaning of four pseudowords that referred to movements of left and right hands and feet. The other four pseudowords did not require any movement and thus were not associated with any meaning. Familiarization with novel pseudowords led to a bilateral repetition suppression of cortical responses to them; the effect started before or around the uniqueness point and lasted for more than 500 ms. After learning, response amplitude to pseudowords that acquired meaning was greater compared with response amplitude to pseudowords that were not assigned meaning; the effect was significant within 144-362 ms after the uniqueness point, and it was found only in the left hemisphere. Within this time interval, a learning-related selective response initially emerged in cortical areas surrounding the Sylvian fissure: anterior superior temporal sulcus, ventral premotor cortex, the anterior part of intraparietal sulcus and insula. Later within this interval, activation additionally spread to more anterior higher-tier brain regions, and reached the left temporal pole and the triangular part of the left inferior frontal gyrus extending to its orbital part. Altogether, current findings evidence rapid plastic changes in cortical representations of meaningful auditory word-forms occurring almost immediately after learning. Additionally, our results suggest that familiarization resulting from stimulus repetition and semantic acquisition resulting from an active learning procedure have separable effects on cortical activity.

Referent's Lexical Frequency Predicts Mismatch Negativity Responses to New Words Following Semantic Training

Lexical ERPs (event-related potentials) obtained in an oddball paradigm were suggested to be an index of the formation of new word representations in the brain in the learning process: with increased exposure to new lexemes, the ERP amplitude grows, which is interpreted as a signature of a new memory-trace build-up and activation. Previous learning studies using this approach have, however, mostly used meaningless novel word forms; it therefore remains uncertain whether the increased amplitude simply reflects increased familiarity with the new stimulus or is indeed a reflection of a complete word representation. Here, we used the oddball paradigm to measure the mismatch negativity (MMN) responses to novel word forms before and after semantic training, during which they were associated with previously familiar words of either high or low frequency of occurrence. Following training, the amplitude of the MMN to novel words was enhanced. Furthermore, these changes were dependent on the frequency of the reference which novel items became associated with: namely, the MMN amplitude became greater and the latency shorter for the item which was assigned the high-frequency meaning. Even though the amount of training was the same for both types of items, the low-frequency stimulus did not achieve similar significant changes. Our results suggest that the new surface form becomes linked to the existing representation, which then automatically activates in full when the respective stimulus is present at the input. This finding indicates that the learning-related MMN dynamics, manifest as a response increase after learning, likely reflects the formation and activation of a complete lexicosemantic memory circuits for words.

Conflict Resolution Ability in Late Bilinguals Improves With Increased Second-Language Proficiency: ANT Evidence

Experimental data supporting the claim that bilingual speakers have superior cognitive control abilities are often questioned with respect to certain methodological limitations. One such limitation is the use of between-group design, potentially confounding bilingual status with other factors (e.g., socioeconomic status). Here, we used a homogeneous sample of 57 young adult Russian-English late unbalanced bilinguals who were administrated Attention Network Task (ANT) together with an L2 proficiency task. We tested the correlation of L2 vocabulary performance with conflict and alertness measures and overall reaction times in ANT performance. Overall, participants demonstrated better conflict resolution with the increase in their second language competence, with 8% of variance in conflict resolution explained by L2 proficiency. Our results support the notion of regular correspondence between bilingualism and cognitive control.

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.

Formation of neocortical memory circuits for unattended written word forms: neuromagnetic evidence

To master linguistic communication, humans must acquire large vocabularies quickly and effortlessly. Efficient word learning might be facilitated by the ability to rapidly acquire novel word forms even outside the focus of attention, occurring within minutes of repetitive exposure and suggesting fast and automatic lexicon acquisition. However, this phenomenon has been studied in the auditory modality only, and it is unknown whether similar mechanisms also exist in the visual domain. We tested this by presenting participants with novel written word forms while the focus of their attention was on a non-linguistic dual colour-detection task. Matched familiar word forms served as a control. Using magnetoencephalography (MEG), we scrutinised changes in neuromagnetic responses to familiar and to novel word forms over approximately 15 minutes of exposure. We found, for the first time, a visual analogue of automatic rapid build-up of neural memory circuits for unattended novel lexical items, seen as a rapid enhancement of early (~100 ms post-onset) activation in the left anterior-superior temporal lobe. Our results suggest that the brain quickly forms cortical representations for new written forms, and indicate that the automatic neural mechanisms subserving rapid online acquisition of novel linguistic information might be shared by both auditory and visual modalities.

The protective properties of Act-Belong-Commit indicators against incident depression, anxiety, and cognitive impairment among older Irish adults: Findings from a prospective community-based study

The Act-Belong-Commit campaign is the world's first comprehensive, population-wide, community-based program designed to promote mental health. The campaign targets individuals to engage in mentally healthy activities, while at the same time, encouraging community organizations that offer such activities, to increase participation in their activities. Using nationally-representative data from Ireland, the aim of this study was to prospectively assess the association between indicators of the Act-Belong-Commit behavioral domains and incident depression, anxiety, and cognitive impairment. Data from two consecutive waves of the Irish Longitudinal Study on Ageing (TILDA) were analyzed. The analytical sample consisted of 6098 adults aged ≥50years. Validated scales for depression, anxiety, and cognitive impairment were used. The number of social/recreational activities engaged in was used as an indicator of Act, social network integration as an indicator of Belong, and frequency of participation in these social/recreational activities as an indicator of Commit. Multivariable logistic regression analyses were conducted to assess associations between baseline indicators of Act-Belong-Commit and incident depression, anxiety, and cognitive impairment at two-year follow-up. The adjusted model showed that each increase in the number of social/recreational activities (Act) inversely predicted the onset of depression, anxiety, and cognitive impairment. The same was the case for social network integration (Belong); that is, being well integrated into social networks was a significant protective factor against all mental health outcomes. Finally, frequency of participation in social/recreational activities (Commit) significantly and inversely predicted the onset of depression and anxiety, while the protective effect against cognitive impairment was only marginally significant. Act-Belong-Commit indicators are shown to be protective against mental disorders and cognitive impairment among older Irish adults. This provides further evidence for the campaign's potential efficacy and has potentially wide-ranging implications for preventing the deterioration of mental health and cognitive decline in the aging community.