Switching off: disruptive TMS reveals distinct contributions of the posterior middle temporal gyrus and angular gyrus to bilingual speech production.

The role of the left temporoparietal cortex in speech production has been extensively studied during native language processing, proving crucial in controlled lexico-semantic retrieval under varying cognitive demands. Yet, its role in bilinguals, fluent in both native and second languages, remains poorly understood. Here, we employed continuous theta burst stimulation to disrupt neural activity in the left posterior middle-temporal gyrus (pMTG) and angular gyrus (AG) while Italian-Friulian bilinguals performed a cued picture-naming task. The task involved between-language (naming objects in Italian or Friulian) and within-language blocks (naming objects ["knife"] or associated actions ["cut"] in a single language) in which participants could either maintain (non-switch) or change (switch) instructions based on cues. During within-language blocks, cTBS over the pMTG entailed faster naming for high-demanding switch trials, while cTBS to the AG elicited slower latencies in low-demanding non-switch trials. No cTBS effects were observed in the between-language block. Our findings suggest a causal involvement of the left pMTG and AG in lexico-semantic processing across languages, with distinct contributions to controlled vs. "automatic" retrieval, respectively. However, they do not support the existence of shared control mechanisms within and between language(s) production. Altogether, these results inform neurobiological models of semantic control in bilinguals.

Sniffing out meaning: Chemosensory and semantic neural network changes in sommeliers.

Wine tasting is a very complex process that integrates a combination of sensation, language, and memory. Taste and smell provide perceptual information that, together with the semantic narrative that converts flavor into words, seem to be processed differently between sommeliers and naïve wine consumers. We investigate whether sommeliers' wine experience shapes only chemosensory processing, as has been previously demonstrated, or if it also modulates the way in which the taste and olfactory circuits interact with the semantic network. Combining diffusion-weighted images and fMRI (activation and connectivity) we investigated whether brain response to tasting wine differs between sommeliers and nonexperts (1) in the sensory neural circuits representing flavor and/or (2) in the neural circuits for language and memory. We demonstrate that training in wine tasting shapes the microstructure of the left and right superior longitudinal fasciculus. Using mediation analysis, we showed that the experience modulates the relationship between fractional anisotropy and behavior: the higher the fractional anisotropy the higher the capacity to recognize wine complexity. In addition, we found functional differences between sommeliers and naïve consumers affecting the flavor sensory circuit, but also regions involved in semantic operations. The former reflects a capacity for differential sensory processing, while the latter reflects sommeliers' ability to attend to relevant sensory inputs and translate them into complex verbal descriptions. The enhanced synchronization between these apparently independent circuits suggests that sommeliers integrated these descriptions with previous semantic knowledge to optimize their capacity to distinguish between subtle differences in the qualitative character of the wine.

Decoding bilingualism from resting-state oscillatory network organization.

Can lifelong bilingualism be robustly decoded from intrinsic brain connectivity? Can we determine, using a spectrally resolved approach, the oscillatory networks that better predict dual-language experience? We recorded resting-state magnetoencephalographic activity in highly proficient Spanish-Basque bilinguals and Spanish monolinguals, calculated functional connectivity at canonical frequency bands, and derived topological network properties using graph analysis. These features were fed into a machine learning classifier to establish how robustly they discriminated between the groups. The model showed excellent classification (AUC: 0.91 ± 0.12) between individuals in each group. The key drivers of classification were network strength in beta (15-30 Hz) and delta (2-4 Hz) rhythms. Further characterization of these networks revealed the involvement of temporal, cingulate, and fronto-parietal hubs likely underpinning the language and default-mode networks (DMNs). Complementary evidence from a correlation analysis showed that the top-ranked features that better discriminated individuals during rest also explained interindividual variability in second language (L2) proficiency within bilinguals, further supporting the robustness of the machine learning model in capturing trait-like markers of bilingualism. Overall, our results show that long-term experience with an L2 can be "brain-read" at a fine-grained level from resting-state oscillatory network organization, highlighting its pervasive impact, particularly within language and DMN networks.

Early language dissociation in bilingual minds: magnetoencephalography evidence through a machine learning approach.

Does neural activity reveal how balanced bilinguals choose languages? Despite using diverse neuroimaging techniques, prior studies haven't provided a definitive solution to this problem. Nonetheless, studies involving direct brain stimulation in bilinguals have identified distinct brain regions associated with language production in different languages. In this magnetoencephalography study with 45 proficient Spanish-Basque bilinguals, we investigated language selection during covert picture naming and word reading tasks. Participants were prompted to name line drawings or read words if the color of the stimulus changed to green, in 10% of trials. The task was performed either in Spanish or Basque. Despite similar sensor-level evoked activity for both languages in both tasks, decoding analyses revealed language-specific classification ~100 ms post-stimulus onset. During picture naming, right occipital-temporal sensors predominantly contributed to language decoding, while left occipital-temporal sensors were crucial for decoding during word reading. Cross-task decoding analysis unveiled robust generalization effects from picture naming to word reading. Our methodology involved a fine-grained examination of neural responses using magnetoencephalography, offering insights into the dynamics of language processing in bilinguals. This study refines our understanding of the neural underpinnings of language selection and bridges the gap between non-invasive and invasive experimental evidence in bilingual language production.

Does bilingual experience influence statistical language learning?

Statistical language learning (SL) tasks measure different aspects of foreign language learning. Studies have used SL tasks to investigate whether bilingual experience confers advantages in acquiring additional languages through implicit processes. However, the results have been inconsistent, which may be related to bilingualism-related features (e.g., degree of dissimilarity between the specific language pair) and other variables such as specific processes that are targeted by the SL task. In the present study, we compared the performance of one Spanish monolingual and two bilingual (Spanish-Basque and Spanish-English) groups across three well-established SL tasks. Each task targeted a different aspect of foreign language learning; specifically, word segmentation, morphological rule generalization, and word-referent learning. In Experiment 1, we manipulated sub-lexical phonotactic patterns to vary the difficulty of three SL tasks, with the results showing no differences between the groups in word segmentation. In Experiment 2, we included non-adjacent dependencies to target affixal morphology rule learning, but again no group-related differences were found. In Experiment 3, we addressed word learning using an audio-visual SL task combining exclusive and multiple word-referent mappings, and found that bilinguals outperformed monolinguals, suggesting that bilingualism may exert influences on SL at the lexical level. This advantage might have been mediated by the high working memory demands required to perform the task. Summarizing, this study shows no evidence for a general bilingual advantage in SL, although bilinguals may outperform monolinguals under specific experimental conditions such as SL tasks that place high demands on working memory processes. In addition, the similar performance of Spanish-Basque and Spanish-English bilinguals across all three SL tasks suggests that the degree of dissimilarity between pairs of spoken languages does not modulate SL skills.

Word frequency and reading demands modulate brain activation in the inferior frontal gyrus.

Processing efficiency differs between high- and low-frequency words, with less frequent words resulting in longer response latencies in several linguistic behavioral tasks. Nevertheless, studies using functional MRI to investigate the word frequency effect have employed diverse methodologies and produced heterogeneous results. In this study, we examine the effect of word frequency through complementary analytical approaches and functional connectivity analyses. Furthermore, we examine whether reading demands, which have been shown to influence reading-related activation, modulate the effects of word frequency. We conducted MRI scanning on 54 healthy participants who performed two versions of a single-word reading task involving high- and low-frequency words: a low-level perceptual reading task and a high-level semantic reading task. The results indicate that word frequency influenced the activation of the pars orbitalis and pars triangularis of the inferior frontal gyrus, but only in the semantic reading task. Additionally, the ventral occipitotemporal cortex exhibited stronger regional activation during the semantic reading task compared to the perceptual reading task, with no effects of word frequency. Functional connectivity analyses demonstrated significant coupling among regions within both the dorsal and ventral reading networks, without any observable effects of word frequency or task. These findings were consistent across group- and individual-level analytical approaches. Overall, our results provide further support for the involvement of the inferior frontal gyrus in semantic processing during reading, as indicated by the effect of word frequency and the influence of reading demands, highlighting the role of the ventral reading network. These findings are discussed in line with their implications for lexical and pre-lexical reading processing.

A novel cognitive neurosurgery approach for supramaximal resection of non-dominant precuneal gliomas: a case report.

Despite mounting evidence pointing to the contrary, classical neurosurgery presumes many cerebral regions are non-eloquent, and therefore, their excision is possible and safe. This is the case of the precuneus and posterior cingulate, two interacting hubs engaged during various cognitive functions, including reflective self-awareness; visuospatial and sensorimotor processing; and processing social cues. This inseparable duo ensures the cortico-subcortical connectivity that underlies these processes. An adult presenting a right precuneal low-grade glioma invading the posterior cingulum underwent awake craniotomy with direct electrical stimulation (DES). A supramaximal resection was achieved after locating the superior longitudinal fasciculus II. During surgery, we found sites of positive stimulation for line bisection and mentalizing tests that enabled the identification of surgical corridors and boundaries for lesion resection. When post-processing the intraoperative recordings, we further identified areas that positively responded to DES during the trail-making and mentalizing tests. In addition, a clear worsening of the patient's self-assessment ability was observed throughout the surgery. An awake cognitive neurosurgery approach allowed supramaximal resection by reaching the cortico-subcortical functional limits. The mapping of complex functions such as social cognition and self-awareness is key to preserving patients' postoperative cognitive health by maximizing the ability to resect the lesion and surrounding areas.

Decoding numeracy and literacy in the human brain: insights from MEG and MVPA.

Numbers and letters are the fundamental building blocks of our everyday social interactions. Previous studies have focused on determining the cortical pathways shaped by numeracy and literacy in the human brain, partially supporting the hypothesis of distinct perceptual neural circuits involved in the visual processing of the two categories. In this study, we aim to investigate the temporal dynamics for number and letter processing. We present magnetoencephalography (MEG) data from two experiments (N = 25 each). In the first experiment, single numbers, letters, and their respective false fonts (false numbers and false letters) were presented, whereas, in the second experiment, numbers, letters, and their respective false fonts were presented as a string of characters. We used multivariate pattern analysis techniques (time-resolved decoding and temporal generalization), testing the strong hypothesis that the neural correlates supporting letter and number processing can be logistically classified as categorically separate. Our results show a very early dissociation (~ 100 ms) between numbers, and letters when compared to false fonts. Number processing can be dissociated with similar accuracy when presented as isolated items or strings of characters, while letter processing shows dissociable classification accuracy for single items compared to strings. These findings reinforce the evidence indicating that early visual processing can be differently shaped by the experience with numbers and letters; this dissociation is stronger for strings compared to single items, thus showing that combinatorial mechanisms for numbers and letters could be categorically distinguished and influence early visual processing.

Cognitive reserve counteracts typical neural activity changes related to ageing.

Studies have shown that older adults with high Cognitive Reserve (HCR) exhibit better executive functioning than their low CR (LCR) counterparts. However, the neural processes linked to those differences are unclear. This study investigates (1) the neural processes underlying executive functions in older adults with HCR compared to older adults with LCR and (2) how executive control differences between HCR and LCR groups are modulated by increased task difficulty. We recruited 74 participants (37 in each group) with diverse CR levels, as determined by a standardised CR questionnaire. Participants performed two executive control tasks with lower and higher difficulty levels (i.e., Simon and spatial Stroop tasks, respectively) while recording the electroencephalogram. The accuracy on both tasks requiring inhibition of irrelevant information was better in the HCR than the LCR group. Also, in the task with higher difficulty level (i.e., the spatial Stroop task), event-related potential (ERP) latencies associated with inhibition (i.e., frontal N200) and updating of working memory (i.e., P300) were earlier in HCR than LCR. Moreover, the HCR, but not the LCR group, showed larger P300 amplitude in parietal than frontal regions and in the left than right hemisphere, suggesting a posterior to anterior shift of activity and loss of inter-hemispheric asymmetries in LCR participants. These results suggest that high CR counteracts neural activity changes related to ageing. Thus, high levels of CR may be related to maintenance of neural activity patterns typically observed in young adults rather than to deployment of neural compensatory mechanisms.

Behavioral and oscillatory signatures of switch costs in highly proficient bilinguals.

Bilinguals with a high proficiency in their first (L1) and second language (L2) often show comparable reaction times when switching from their L1 to L2 and vice-versa ("symmetrical switch costs"). However, the neurophysiological signatures supporting this effect are not well understood. Here, we ran two separate experiments and assessed behavioral and MEG responses in highly proficient Spanish-Basque bilinguals while they overtly name pictures in a mixed-language context. In the behavioral experiment, bilinguals were slower when naming items in switch relative to non-switch trials, and this switch cost was comparable for both languages (symmetrical). The MEG experiment mimicked the behavioral one, with switch trials showing more desynchronization than non-switch trials across languages (symmetric neural cost) in the alpha band (8-13 Hz). Source-localization revealed the engagement of right parietal and premotor areas, which have been linked to language selection and inhibitory control; and of the left anterior temporal lobe (ATL), a cross-linguistic region housing conceptual knowledge that generalizes across languages. Our results suggest that highly proficient bilinguals implement a language-independent mechanism, supported by alpha oscillations, which is involved in cue-based language selection and facilitates conceptually-driven lexical access in the ATL, possibly by inhibiting non-target lexical items or disinhibiting target ones.

Brain structure, phenotypic and genetic correlates of reading performance.

Reading is an evolutionarily recent development that recruits and tunes brain circuitry connecting primary- and language-processing regions. We investigated whether metrics of the brain's physical structure correlate with reading performance and whether genetic variants affect this relationship. To this aim, we used the Adolescent Brain Cognitive Development dataset (n = 9,013) of 9-10-year-olds and focused on 150 measures of cortical surface area (CSA) and thickness. Our results reveal that reading performance is associated with nine measures of brain structure including relevant regions of the reading network. Furthermore, we show that this relationship is partially mediated by genetic factors for two of these measures: the CSA of the entire left hemisphere and, specifically, of the left superior temporal gyrus CSA. These effects emphasize the complex and subtle interplay between genes, brain and reading, which is a partly heritable polygenic skill that relies on a distributed network.

Morphological decomposition in Chinese compound word recognition: Electrophysiological evidence.

The present study examined the effect of both morphological complexity and semantic transparency in Chinese compound word recognition. Using a visual lexical decision task, our electrophysiological results showed that transparent and opaque compounds induced stronger Left Anterior Negativity (LAN) than monomorphemic words. This result suggests that Chinese compounds might be decomposed into their constituent morphemes at the lemma level, whereas monomorphemic words are accessed as a whole-word lemma directly from the form level. In addition, transparent and opaque compounds produced a similar N400 as each other, suggesting that transparency did not show an effect on the involvement of constituent morphemes during access to the whole-word lemma. Two behavioral experiments additionally showed similar patterns to the EEG results. These findings support morphological decomposition for compounds at the lemma level as proposed by the full-parsing model, and no evidence is found to support the role of transparency during Chinese compound word recognition.

Theta-gamma phase-amplitude coupling in auditory cortex is modulated by language proficiency.

The coordination between the theta phase (3-7 Hz) and gamma power (25-35 Hz) oscillations (namely theta-gamma phase-amplitude coupling, PAC) in the auditory cortex has been proposed as an essential neural mechanism involved in speech processing. However, it has not been established how this mechanism is related to the efficiency with which a listener processes speech. Speech processing in a non-native language offers a useful opportunity to evaluate if theta-gamma PAC is modulated by the challenges imposed by the reception of speech input in a non-native language. The present study investigates how auditory theta-gamma PAC (recorded with magnetoencephalography) is modulated in both native and non-native speech reception. Participants were Spanish native (L1) speakers studying Basque (L2) at three different levels: beginner (Grade 1), intermediate (Grade 2), and advanced (Grade 3). We found that during L2 speech processing (i) theta-gamma PAC was more highly coordinated for intelligible compared to unintelligible speech; (ii) this coupling was modulated by proficiency in Basque being lower for beginners, higher for intermediate, and highest for advanced speakers (no difference observed in Spanish); (iii) gamma power did not differ between languages and groups. These findings highlight how the coordinated theta-gamma oscillatory activity is tightly related to speech comprehension: the stronger this coordination is, the more the comprehension system will proficiently parse the incoming speech input.

"Neural dynamics supporting longitudinal plasticity of action naming across languages: MEG evidence from bilingual brain tumor patients".

Previous evidence suggests that distinct ventral and dorsal streams respectively underpin the semantic processing of object and action knowledge. Recently, we found that brain tumor patients with dorsal gliomas in frontoparietal hubs show a selective longitudinal compensation (post-vs. pre-surgery) during the retrieval of lexico-semantic information about actions (but not objects), indexed by power increases in beta rhythms (13-28 Hz). Here, we move one-step further and ask whether a similar organizational principle also stands across the different languages a bilingual speaks. To test this hypothesis, we combined a picture-naming task with MEG recordings and evaluated highly proficient Spanish-Basque bilinguals undergoing surgery for tumor resection in left frontoparietal regions. We assessed patients before and three months after surgery. At the behavioral level, we observed a similar performance across sessions irrespectively of the language at use, suggesting overall successful function preservation. At the oscillatory level, we found longitudinal selective power increases in beta for action naming in Spanish and Basque. Nevertheless, tumor resection triggered a differential reorganization of the L1 and the L2, with the latter one additionally recruiting the right hemisphere. Overall, our results provide evidence for (i) the specific involvement of frontoparietal regions in the semantic retrieval/representation of action knowledge across languages; (ii) a key role of beta oscillations as a signature of language compensation and (iii) the existence of divergent plasticity trajectories in L1 and L2 after surgery. By doing so, they provide new insights into the spectro-temporal dynamics supporting postoperative recovery in the bilingual brain.

Verbal production dynamics and plasticity: functional contributions of language and executive control systems.

Bilingual language production requires both language knowledge and language control in order to communicate in a target language. Learning or improving a language in adulthood is an increasingly common undertaking, and this has complex effects on the cognitive and neural processes underlying language production. The current functional magnetic resonance imaging (fMRI) experiment investigated the functional plasticity of verbal production in adult language learners, and examined the dynamics of word retrieval in order to dissociate the contributions of language knowledge and executive control. Thirty four adults who were either intermediate or advanced language learners, underwent MRI scanning while performing verbal fluency tasks in their native and new languages. A multipronged analytical approach revealed (i) time-varying contributions of language knowledge and executive control to verbal fluency performance, (ii) learning-related changes in the functional correlates of verbal fluency in both the native and new languages, (iii) no effect of learning on lateralization, and (iv) greater functional coupling between language and language control regions with greater second language experience. Collectively, our results point to significant functional plasticity in adult language learners that impacts the neural correlates of production in both the native and new languages, and provide new insight into the widely used verbal fluency task.

Cross-modal and cross-language activation in bilinguals reveals lexical competition even when words or signs are unheard or unseen.

We exploit the phenomenon of cross-modal, cross-language activation to examine the dynamics of language processing. Previous within-language work showed that seeing a sign coactivates phonologically related signs, just as hearing a spoken word coactivates phonologically related words. In this study, we conducted a series of eye-tracking experiments using the visual world paradigm to investigate the time course of cross-language coactivation in hearing bimodal bilinguals (Spanish-Spanish Sign Language) and unimodal bilinguals (Spanish/Basque). The aim was to gauge whether (and how) seeing a sign could coactivate words and, conversely, how hearing a word could coactivate signs and how such cross-language coactivation patterns differ from within-language coactivation. The results revealed cross-language, cross-modal activation in both directions. Furthermore, comparison with previous findings of within-language lexical coactivation for spoken and signed language showed how the impact of temporal structure changes in different modalities. Spoken word activation follows the temporal structure of that word only when the word itself is heard; for signs, the temporal structure of the sign does not govern the time course of lexical access (location coactivation precedes handshape coactivation)-even when the sign is seen. We provide evidence that, instead, this pattern of activation is motivated by how common in the lexicon the sublexical units of the signs are. These results reveal the interaction between the perceptual properties of the explicit signal and structural linguistic properties. Examining languages across modalities illustrates how this interaction impacts language processing.

Mind the orthography: Revisiting the contribution of prereading phonological awareness to reading acquisition.

Reading acquisition is based on a set of preliteracy skills that lay the foundation for future reading abilities. Phonological awareness-the ability to identify and manipulate the sound units of oral language-has been reported to play a central role in reading acquisition. However, current evidence is mixed with respect to its universal contribution to reading acquisition across orthographies. This longitudinal study examines the development and contribution of phonological awareness to early reading skills in Spanish, a transparent orthography. The results of a comprehensive battery of phonological awareness skills in a large sample of children (Time 1 n = 616, 296 females, mean age 5.6, from middle to high socioeconomic backgrounds; Time 2 n = 397) with no reading experience at study onset suggest that the development of phonological awareness is delayed in Spanish. Furthermore, our results show that phonological awareness does not contribute to the prediction of reading acquisition above and beyond other preliteracy skills. Letter knowledge indexes children's ability to identify phonemes and thus takes a more central role in the prediction of early reading skills. Therefore, we underscore the need to thoughtfully address the distinctive features of the reading acquisition process across orthographies, which should be taken into account in models of reading and learning to read. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Open access dataset of task-free hemodynamic activity in 4-month-old infants during sleep using fNIRS.

Spontaneous, task-free, hemodynamic activity of the brain provides useful information about its functional organization, as it can describe how different brain regions communicate to each other. Neuroimaging studies measuring the spontaneous activity of the brain are conducted while the participants are not engaged in a particular task or receiving any external stimulation. This approach is particularly useful in developmental populations as brain activity can be measured without the need for infant compliance and the risks of data contamination due to motion artifacts. In this project we sought to i) characterize the intrinsic functional organization of the brain in 4-month-old infants and ii) investigate whether bilingualism, as a specific environmental factor, could lead to adaptations on functional brain network development at this early age. Measures of spontaneous hemodynamic activity were acquired in 4-month-old infants (n = 104) during natural sleep using functional near-infrared spectroscopy (fNIRS). Emphasis was placed on acquiring high-quality data that could lead to reproducible results and serve as a valuable resource for researchers investigating the developing functional connectome.