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.

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.

Oscillatory and structural signatures of language plasticity in brain tumor patients: A longitudinal study.

Recent evidence suggests that damage to the language network triggers its functional reorganization. Yet, the spectro-temporal fingerprints of this plastic rearrangement and its relation to anatomical changes is less well understood. Here, we combined magnetoencephalographic recordings with a proxy measure of white matter to investigate oscillatory activity supporting language plasticity and its relation to structural reshaping. First, cortical dynamics were acquired in a group of healthy controls during object and action naming. Results showed segregated beta (13-28 Hz) power decreases in left ventral and dorsal pathways, in a time-window associated to lexico-semantic processing (~250-500 ms). Six patients with left tumors invading either ventral or dorsal regions performed the same naming task before and 3 months after surgery for tumor resection. When longitudinally comparing patients' responses we found beta compensation mimicking the category-based segregation showed by controls, with ventral and dorsal damage leading to selective compensation for object and action naming, respectively. At the structural level, all patients showed preoperative changes in white matter tracts possibly linked to plasticity triggered by tumor growth. Furthermore, in some patients, structural changes were also evident after surgery and showed associations with longitudinal changes in beta power lateralization toward the contralesional hemisphere. Overall, our findings support the existence of anatomo-functional dependencies in language reorganization and highlight the potential role of oscillatory markers in tracking longitudinal plasticity in brain tumor patients. By doing so, they provide valuable information for mapping preoperative and postoperative neural reshaping and plan surgical strategies to preserve language function and patient's quality of life.

MULTIMAP: Multilingual picture naming test for mapping eloquent areas during awake surgeries.

Picture naming tasks are currently the gold standard for identifying and preserving language-related areas during awake brain surgery. With multilingual populations increasing worldwide, patients frequently need to be tested in more than one language. There is still no reliable testing instrument, as the available batteries have been developed for specific languages. Heterogeneity in the selection criteria for stimuli leads to differences, for example, in the size, color, image quality, and even names associated with pictures, making direct cross-linguistic comparisons difficult. Here we present MULTIMAP, a new multilingual picture naming test for mapping eloquent areas during awake brain surgery. Recognizing that the distinction between nouns and verbs is necessary for detailed and precise language mapping, MULTIMAP consists of a database of 218 standardized color pictures representing both objects and actions. These images have been tested for name agreement with speakers of Spanish, Basque, Catalan, Italian, French, English, German, Mandarin Chinese, and Arabic, and have been controlled for relevant linguistic features in cross-language combinations. The MULTIMAP test for objects and verbs represents an alternative to the Oral Denomination 80 (DO 80) monolingual pictorial set currently used in language mapping, providing an open-source, standardized set of up-to-date pictures, where relevant linguistic variables across several languages have been taken into account in picture creation and selection.

Neglectful maternal caregiving involves altered brain volume in empathy-related areas.

The maternal brain undergoes adaptations to sensitive caregiving that are critical for infant well-being. We investigated structural alterations associated with neglectful caregiving and their effects on mother-child interactive behavior. High-resolution 3D volumetric images were obtained on 25 neglectful (NM) and 23 non-neglectful control (CM) mothers. Using voxel-based morphometry, we compared differences in gray and white matter (GM and WM, respectively) volume. Mothers completed an empathy scale and participated with their children in a play task (Emotional Availability Scale, EA). Neglectful mothers showed smaller GM volume in the right insula, anterior/middle cingulate (ACC/MCC), and right inferior frontal gyrus and less WM volume in bilateral frontal regions than did CM. A greater GM volume was observed in the right fusiform and cerebellum in NM than in CM. Regression analyses showed a negative effect of greater fusiform GM volume and a positive effect of greater right frontal WM volume on EA. Mediation analyses showed the role of emotional empathy in the positive effect of the insula and right inferior frontal gyrus and in the negative effect of the cerebellum on EA. Neglectful mothering involves alterations in emotional empathy-related areas and in frontal areas associated with poor mother-child interactive bonding, indicating how critical these areas are for sensitive caregiving.

Tracing the interplay between syntactic and lexical features: fMRI evidence from agreement comprehension.

The current fMRI study was designed to investigate whether the processing of different gender-related cues embedded in nouns affects the computation of agreement dependencies and, if so, where this possible interaction is mapped in the brain. We used the Spanish gender agreement system, which makes it possible to manipulate two different factors: the agreement between different sentence constituents (i.e., by contrasting congruent versus incongruent determiner-noun pairs) and the formal (i.e., orthographical/morphological) and/or lexical information embedded in the noun -i.e., by contrasting transparent (e.g., libromasc. [book]; lunafem. [moon]) and opaque nouns (e.g., lápizmasc. [pencil]; vejezfem. [old age]). Crucially, these data illustrated, for the first time, how the network underlying agreement is sensitive to different gender-to-ending cues: different sources of gender information associated with nouns affect the neural circuits involved in the computation of local agreement dependencies. When the gender marking is informative (as in the case of transparent nouns), both formal and lexical information is used to establish grammatical relations. In contrast, when no formal cues are available (as in the case of opaque nouns), gender information is retrieved from the lexicon. We demonstrated the involvement of the posterior MTG/STG, pars triangularis within the IFG, and parietal regions during gender agreement computation. Critically, in order to integrate the different available information sources, the dynamics of this fronto-temporal loop change and additional regions, such as the hippocampus, the angular and the supramarginal gyri are recruited. These results underpin previous neuroanatomical models proposed in the context of both gender processing and sentence comprehension. But, more importantly, they provide valuable information regarding how and where the brain's language system dynamically integrates all the available form-based and lexical cues during comprehension.

Orthographic Coding: Brain Activation for Letters, Symbols, and Digits.

The present experiment investigates the input coding mechanisms of 3 common printed characters: letters, numbers, and symbols. Despite research in this area, it is yet unclear whether the identity of these 3 elements is processed through the same or different brain pathways. In addition, some computational models propose that the position-in-string coding of these elements responds to general flexible mechanisms of the visual system that are not character-specific, whereas others suggest that the position coding of letters responds to specific processes that are different from those that guide the position-in-string assignment of other types of visual objects. Here, in an fMRI study, we manipulated character position and character identity through the transposition or substitution of 2 internal elements within strings of 4 elements. Participants were presented with 2 consecutive visual strings and asked to decide whether they were the same or different. The results showed: 1) that some brain areas responded more to letters than to numbers and vice versa, suggesting that processing may follow different brain pathways; 2) that the left parietal cortex is involved in letter identity, and critically in letter position coding, specifically contributing to the early stages of the reading process; and that 3) a stimulus-specific mechanism for letter position coding is operating during orthographic processing.

Verbal and nominal agreement: An fMRI study.

Agreement computation is one of the pillars of language comprehension. In this fMRI study, we investigated the neuro-cognitive processes of agreement associated with number feature covariance in subject-verb agreement and determiner-noun concord in Spanish by creating mismatches (ella/*ellas corre, she/*they dances vs. el/*los anillo, thesg/*thepl ring). The results evidenced the engagement of a common bilateral fronto-parietal monitoring system, not language specific, and a left fronto-temporal system that seems to be specifically related to different aspects of phrase and sentence processing. In particular, the major difference was found in the anterior portion of the left MTG-STG, which we relate to fine-grained syntactic-combinatorial building mechanisms apparently controlled by the pars opercularis within the LIFG. These results suggest that general conflict-monitoring processes operate in parallel with language-specific mechanisms that are sensitive to the specificity of agreement type for the detection of feature covariance among sentence constituents. Specifically, the coupling between these frontal and temporal regions seems to be flexible enough to show sensitivity to the fine-grained combinatorial mechanisms that underlie nominal and subject-verb agreement.

Where agreement merges with disagreement: fMRI evidence of subject-verb integration.

Language comprehension is incremental, involving the integration of information from different words together with the need to resolve conflicting cues when unexpected information occurs. The present fMRI design seeks to segregate the neuro-anatomical substrates of these two processes by comparing well-formed and ill-formed sentences during subject-verb agreement computation. Our experiment takes advantage of a particular Spanish feature, the Unagreement phenomenon: a subject-verb agreement mismatch that results in a grammatical sentence ("Los pintores trajimos…" [The painters3.pl (we)brought1.pl…]). Comprehension of this construction implies a shift in the semantic interpretation of the subject from 3rd-person to 1st-person, enabling the phrase "The painters" to be re-interpreted as "We painters". Our results include firstly a functional dissociation between well-formed and ill-formed sentences with Person Mismatches: while Person Mismatches recruited a fronto-parietal network associated to monitoring operations, grammatical sentences (both Unagreement and Default Agreement) recruited a fronto-temporal network related to syntactic-semantic integration. Secondly, there was activation in the posterior part of the left middle frontal gyrus for both Person Mismatches and Unagreement, reflecting the evaluation of the morpho-syntactic match between agreeing constituents. Thirdly, the left angular gyrus showed increased activation only for Unagreement, highlighting its crucial role in the comprehension of semantically complex but non-anomalous constructions. These findings point to a central role of the classic fronto-temporal network, plus two additional nodes: the posterior part of the left middle frontal gyrus and the left angular gyrus; opening new windows to the study of agreement computation and language comprehension.

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.

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.

Grey matter reshaping of language-related regions depends on tumor lateralization.

A brain tumor in the left hemisphere can decrease language laterality as assessed with fMRI. However, it remains unclear whether or not this decreased language laterality is associated with a structural reshaping of the grey matter, particularly within the language network. Here, we examine if the disruption of language hubs exclusively affects macrostructural properties of contralateral homologues (as suggested by previous research), or whether it affects both hemispheres. This study uses voxel-based morphometry applied to high-resolution MR T1-weighted MPRAGE images from 31 adult patients left-dominant for language. Eighteen patients had brain tumors in the left hemisphere, and 13 had tumors in the right hemisphere. A cohort of 71 healthy individuals matched on age and sex was used as a baseline. We defined 10 ROIs per hemisphere known to subserve language function. Two separate repeated-measures ANOVAs were conducted with the volume per region as the dependent variables. For the patients, tumor lateralization (right versus left) served as a between-subject factor. The current study demonstrated that the presence of a brain tumor generates a global volumetric change affecting left language regions and their contralateral homologues. These changes are mediated by the lateralization of the lesion. Our findings suggest that compensatory functional mechanisms are supported by the rearrangement of the grey matter, although future longitudinal research should determine the temporal course of such changes.

Grey Matter Reshaping of Language-Related Regions Depends on Tumor Lateralization.

A brain tumor in the left hemisphere can decrease language laterality as assessed through fMRI. However, it remains unclear whether or not this decreased language laterality is associated with a structural reshaping of the grey matter, particularly within the language network. Here, we examine if the disruption of the language hubs exclusively affects the macrostructural properties of the contralateral homologues or whether it affects both hemispheres. This study uses voxel-based morphometry applied to high-resolution MR T1-weighted MPRAGE images from 31 adult patients' left hemisphere, which is dominant for language. Eighteen patients had brain tumors in the left hemisphere, and thirteen had tumors in the right hemisphere. A cohort of 71 healthy individuals matched with respect to age and sex was used as a baseline. We defined 10 ROIs per hemisphere involved in language function. Two separate repeated-measure ANOVAs were conducted with the volume per region as the dependent variable. For the patients, tumor lateralization (right versus left) served as a between-subject factor. The current study demonstrated that the presence of a brain tumor generates global volumetric changes affecting the left language regions and their contralateral homologues. These changes are mediated by the lateralization of the lesion. Our findings suggest that functional mechanisms are supported by the rearrangement of the grey matter.

"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.

Oscillatory dynamics underlying noun and verb production in highly proficient bilinguals.

Words representing objects (nouns) and words representing actions (verbs) are essential components of speech across languages. While there is evidence regarding the organizational principles governing neural representation of nouns and verbs in monolingual speakers, little is known about how this knowledge is represented in the bilingual brain. To address this gap, we recorded neuromagnetic signals while highly proficient Spanish-Basque bilinguals performed a picture-naming task and tracked the brain oscillatory dynamics underlying this process. We found theta (4-8 Hz) power increases and alpha-beta (8-25 Hz) power decreases irrespectively of the category and language at use in a time window classically associated to the controlled retrieval of lexico-semantic information. When comparing nouns and verbs within each language, we found theta power increases for verbs as compared to nouns in bilateral visual cortices and cognitive control areas including the left SMA and right middle temporal gyrus. In addition, stronger alpha-beta power decreases were observed for nouns as compared to verbs in visual cortices and semantic-related regions such as the left anterior temporal lobe and right premotor cortex. No differences were observed between categories across languages. Overall, our results suggest that noun and verb processing recruit partially different networks during speech production but that these category-based representations are similarly processed in the bilingual brain.

Covert face recognition without the fusiform-temporal pathways.

Patients with prosopagnosia are unable to recognize faces consciously, but when tested indirectly they can reveal residual identification abilities. The neural circuitry underlying this covert recognition is still unknown. One candidate for this function is the partial survival of a pathway linking the fusiform face area (FFA) and anterior-inferior temporal (AIT) cortex, which has been shown to be essential for conscious face identification. Here we performed functional magnetic, and diffusion tensor imaging in FE, a patient with severe prosopagnosia, with the goal of identifying the neural substrates of his robust covert face recognition. FE presented massive bilateral lesions in the fusiform gyri that eliminated both FFAs, and also disrupted the fibers within the inferior longitudinal fasciculi that link the visual areas with the AITs and medial temporal lobes. Therefore participation of the fusiform-temporal pathway in his covert recognition was precluded. However, face-selective activations were found bilaterally in his occipital gyri and in his extended face system (posterior cingulate and orbitofrontal areas), the latter with larger responses for previously-known faces than for faces of strangers. In the right hemisphere, these surviving face selective-areas were connected via a partially persevered inferior fronto-occipital fasciculus. This suggests an alternative occipito-frontal pathway, absent from current models of face processing, that could explain the patient's covert recognition while also playing a role in unconscious processing during normal cognition.

Brain and personality bases of insensitivity to infant cues in neglectful mothers: an event-related potential study.

This investigation examined the neural and personality correlates of processing infant facial expressions in mothers with substantiated neglect of a child under 5 years old. Event-related potentials (ERPs) were recorded from 14 neglectful and 14 control mothers as they viewed and categorized pictures of infant cries, laughs, and neutral faces. Maternal self-reports of anhedonia and empathy were also completed. Early (negative occipitotemporal component peaking at around 170 ms on the scalp [N170] and positive electrical potential peaking at about 200 ms [P200]) and late positive potential (LPP) components were selected. Both groups of mothers showed behavioral discrimination between the different facial expressions via reaction time and accuracy measures. Neglectful mothers did not exhibit increased N170 amplitude at temporal leads in response to viewing crying versus laughing and neutral expressions compared to control mothers. Both groups had greater P200 and LPP amplitudes at centroparietal leads in response to viewing crying versus neutral facial expressions. However, neglectful mothers displayed an overall attenuated brain response in LPP that was related to their higher scores in social anhedonia but not to their empathy scores. The ERP data suggest that the brain's failures in the early differentiation of cry stimuli and in the sustained processing of infant expressions related to social anhedonia may underlie the insensitive responding in neglectful mothers. The implications of these results for the design and evaluation of preventive interventions are discussed.

Distinctive Frontal and Occipitotemporal Surface Features in Neglectful Parenting.

Although the brain signatures of adaptive human parenting are well documented, the cortical features associated with maladaptive caregiving are underexplored. We investigated whether cortical thickness and surface area vary in a small group of mothers who had neglected their children (24 in the neglect group, NG) compared to a control group of mothers with non-neglectful caregiving (21 in the control group, CG). We also tested whether the cortical differences were related to dyadic mother-child emotional availability (EA) in a play task with their children and whether alexithymia involving low emotional awareness that characterizes the NG could play a role in the cortical-EA associations. Whole-brain analysis of the cortical mantle identified reduced cortical thickness in the right rostral middle frontal gyrus and an increased surface area in the right lingual and lateral occipital cortices for the NG with respect to the CG. Follow-up path analysis showed direct effects of the right rostral middle frontal gyrus (RMFG) on the emotional availability (EA) and on the difficulty to identify feelings (alexithymia factor), with a marginal indirect RMFG-EA effect through this factor. These preliminary findings extend existing work by implicating differences in cortical features associated with neglectful parenting and relevant to mother-child interactive bonding.