Brain and Language

Cross-linguistic activation is unavoidable in bilinguals and they require language control to manage it. In this study, it is posited that Relative Language Distance (RLD; the extent of lexical feature-similarity between bilinguals languages) can affect the extent of cross-linguistic activation and hence influence bilingual language control. This was investigated via an er-fMRI word-translation task on three similar bilingual groups but with varying RLDs: Dutch-English (low-RLD), Hindi-English (intermediate-RLD) and Cantonese-English (high-RLD). Cross-linguistic conflict and the degree of conflict monitoring/control necessary to manage it were expected to increase with decreasing RLD across groups and be appropriately reflected in the activity of conflict monitoring/control neural regions, such as the ACC (anterior cingulate cortex). Analysis revealed a significantly differential ACC response across the groups, reflecting its adaptation to differential conflict monitoring/control demands generated by RLD. The findings provide emerging evidence for RLD as a dimension of bilingualism impacting bilingual language control processes and neurobiology.

The functional organization of first (L1) and second (L2) language processing in bilinguals remains a topic of great interest to the neurolinguistics community. Functional magnetic resonance imaging (fMRI) studies report meaningful differences in the location and extent of hemodynamic changes between tasks performed in the L1 and L2, yet there is no consensus on whether these networks can be considered truly distinct. In part, this may be due to the multiplicity of task designs implemented in such studies, which complicates the interpretation of their findings. This paper compares the results of previous bilingual meta-analyses to a new ALE meta-analysis that categorizes neuroimaging studies by task design. Factors such as the age of L2 acquisition (AoA) and the L2 language proficiency level of participants are also considered. The findings support previous accounts of the effect of participant characteristics on linguistic processing, while at the same time revealing dissociable differences in fMRI activation for L1 and L2 networks within and across tasks that appear independent of these external factors.

Second language (L2) processing engages both language-specific and domain-general control systems, yet how these systems vary with L2 proficiency remains unclear. We used functional magnetic resonance imaging (fMRI) to examine neural activity during L2 English processing in Korean-English (K-E) bilinguals across three proficiency levels (beginner, intermediate, advanced). Participants performed rhyme and spelling judgement tasks manipulating orthographic-phonological conflict. Behaviourally, conflict conditions reduced accuracy, with proficiency effects observed selectively in the rhyme task. fMRI results showed that conflict processing recruited frontoparietal control regions, including inferior frontal and parietal cortices, accompanied by deactivation in default mode network regions. Critically, proficiency-related effects differed by task. During rhyme judgement, advanced bilinguals showed greater activation in the left supramarginal gyrus (SMG) and cerebellum, whereas intermediate bilinguals exhibited greater recruitment of the left middle orbital gyrus and dorsomedial prefrontal cortex. During spelling judgement, advanced bilinguals showed greater thalamic activation alongside greater deactivation of the right dorsolateral prefrontal cortex. Activity in the left SMG and cerebellum was positively associated with L2 reading score, and cerebellar activity was also associated with rhyme-task performance, whereas right DLPFC activity was negatively associated with the scores. These findings suggest that increasing L2 proficiency is associated less with altered recruitment of core reading regions than with task-specific shifts in the balance between phonological-specialized, subcortical attentional, and domain-general control systems supporting L2 processing.

At first glance, the brains language network appears to be universal, but languages clearly differ. How does the brain adapt to the specific details of individual grammatical systems? Here, we present an MEG study on case and agreement in Hindi and Nepali. Both languages use split-ergative case systems. However, these systems interact with verb agreement differently - in Hindi, case features conspire to determine which noun phrase (NP) the verb agrees with (subject, object, or neither), but in Nepali the verb always agrees with the subject NP. We found that left inferior frontal and left anterior temporal regions are sensitive to case features in both languages. Across case configurations, these same brain areas in Hindi participants show different patterns of activity for sentences that require masculine vs. feminine marking on the verb, before the comprehenders encounter it. Additionally, the left temporoparietal junction in Hindi shows different activity for subject and object agreement configurations. Both findings are not observed in Nepali participants. We suggest that this brain response demonstrates a unique-to-Hindi selection of an agreement controller and pre-encoding of the verbs morphological features. This shows that brain activity reflects psycholinguistic processes that are intimately tied to grammatical features. HighlightsO_LIThe left inferior frontal lobe and the left anterior temporal lobe distinguish accusative objects versus bare object NPs in Hindi and Nepali, and pre-emptively encode gender agreement features in Hindi. C_LIO_LIThe left inferior parietal lobe shows a differential sensitivity to object-agreement and subject-agreement constructions in Hindi that is absent in Nepali C_LIO_LIMEG can reveal differences in neural activity that reflect specific requirements of different grammatical systems C_LI

The use of multiple languages modulates the neural mechanisms of selective attention, but it is unclear whether these adaptations require continuous engagement and active second language usage. Here we examined whether language usage shapes selective attention in bilingualism, and what neural processes might this engage. 48 highly proficient English-French bilinguals listened to naturalistic speech streams in their first or second language, paired with either linguistic and non-linguistic interference. Participants were matched on their L2 proficiency, but were either Active, Moderate, or Inactive users of their second language. The results revealed usage-related modulation of oscillatory activity in the alpha band, with more efficient inhibitory control in Active and Moderate users leading to behavioural resilience to interference. In contrast, usage did not affect lower-level perceptual tracking of speech, as captured by mTRF decoding of speech envelopes across frequency bands. Taken together, our findings show that resilience to interference during language processing is not dependent on the perceptual speech tracking, but rather on the capacity to recruit higher-level attentional control mechanisms, a process that is dynamically shaped by bilinguals L2 usage.

In principle, functional neuroimaging provides uniquely informative data in addressing linguistic questions, because it can indicate distinct processes that are not apparent from behavioral data alone. This could involve adjudicating the source of unacceptability via the different patterns of elicited brain responses to different ungrammatical sentence types. However, it is difficult to interpret brain activations to syntactic violations. Such responses could reflect processes that have nothing intrinsically related to linguistic representations, such as domain-general executive function abilities. In order to facilitate the potential use of functional neuroimaging methods to identify the source of different syntactic violations, we conducted an fMRI experiment to identify the brain activation maps associated with two distinct syntactic violation types: phrase structure (created by inverting the order of two adjacent words within a sentence) and subject islands (created by extracting a wh-phrase out of an embedded subject). The comparison of these violations to control sentences surprisingly showed no indication of a generalized violation response, with almost completely divergent activation patterns. Phrase structure violations seemingly activated regions previously implicated in verbal working memory and structural complexity in sentence processing, whereas the subject islands appeared to activate regions previously implicated in conceptual-semantic processing, broadly defined. We review our findings in the context of previous research on syntactic and semantic violations using event- related potentials. Although our results suggest potentially distinct underlying mechanisms underlying phrase structure and subject island violations, our results are tentative and suggest important methodological considerations for future research in this area.

Although psycho-/neuro-linguistics has assumed a distinction between morphological and syntactic structure building as in traditional theoretical linguistics, this distinction has been increasingly challenged by theoretical linguists in recent years. Opposing a sharp, lexicalist distinction between morphology and syntax, non-lexicalist theories propose common morpho-syntactic structure building operations that cut across the realms of "morphology" and "syntax", which are considered distinct territories in lexicalist theories. Taking advantage of two pairs of contrasts in Mandarin Chinese with desirable linguistic properties, namely compound vs. simplex nouns (the "morphology" contrast, differing in morphological structure complexity per lexicalist theories) and separable vs. inseparable verbs (the "syntax" contrast, differing in syntactic structure complexity per lexicalist theories), we report one of the first pieces of evidence for shared neural responses for morphological and syntactic structure complexity in language comprehension, supporting a non-lexicalist view where shared neural computations are employed across morpho-syntactic structure building. Specifically, we observed that the two contrasts both modulated neural responses in left anterior and centro-parietal electrodes in an a priori 275:400 ms time window, corroborated by topographical similarity analyses. These results serve as preliminary yet prima facie evidence towards shared neural computations across morphological and syntactic structure building in language comprehension.

A fundamental question in the cognitive neuroscience of language is how grammatical representations are reflected in the organization and activity of the brain. This is challenging in part because superficial differences between languages, e.g., word order, exert different demands on the memory systems that process these structures. Here, we present an electroencephalography (EEG) study to investigate the brains responses to wh-constructions in English, Urdu, and Mandarin Chinese. In addition to the different word orders, writing systems, and morphological typologies of the 3 languages, these languages diverge with regard to how wh-constructions are formed: English requires filler-gap dependencies for wh-objects, whereas Urdu and Mandarin Chinese do not. We use a rapid parallel reading task, in which short sentences are displayed in parallel for 200ms to mitigate the different demands placed on memory systems. We show that neural responses distinguish wh-object constructions from their controls in midline anterior (Urdu, Mandarin Chinese) and right posterior sensors (English, Mandarin Chinese), from 200-400ms (English, Mandarin Chinese) and 500-800ms (English, Urdu). Although there is no detectable uniform, language-invariant response to wh-constructions across languages, there are a number of shared features in the evoked response between any pair of languages, i.e., wh-in-situ constructions generate an evoked response in midline anterior sensors. Moreover, behavioral evidence shows a robust cross-language cost of processing wh-object constructions, regardless of their surface form. This demonstrates that readers of diverse languages can process some grammatical information in a short 200ms fixation, and that the RPVP methodology may enable new ways of linking cognitive neuroscience of language to comparative syntax, i.e., the systematic description of similarities and differences between grammatical structures.

Prior studies in bilinguals have reported relationships between brain structure and the dimensions of (i) language proficiency or (ii) language balance (the discrepancy between a bilinguals two proficiencies), but rarely both, even though they are highly related. These studies were often conducted in late bilinguals and the analyses limited to regions of interest. Here, we tested for relationships between brain structure and these two dimensions in 46 early cultural Spanish-English bilinguals (mean age = 16.7 years) at the level of the whole brain for gray matter volume (GMV) and cortical thickness (CT). Results revealed a positive association between GMV and proficiency in the weaker language in the right angular gyrus (AG; BA 39) extending into the superior temporal gyrus (BA 22). More balanced bilingualism was also associated with more GMV in the AG (BA 39), in addition to less GMV in left postcentral gyrus (BA 1), right cerebellum lobule IX and right superior occipital gyrus (BA 18). However, these relationships between GMV and balance disappeared after controlling for language proficiency. No significant associations were observed for CT and these two dimensions of language. Our findings suggest that relationships between GMV and balance are driven by language proficiency, and that the relationship between GMV and language proficiency likely does not involve language-specific mechanisms, given the location of the association is in the right inferior parietal cortex. Together, this study separates the neuroanatomical bases of these two language dimensions and places them in brain regions outside those usually targeted in prior studies. HighlightsO_LINeuroanatomy was correlated with proficiencies in early Spanish-English bilinguals C_LIO_LIRight angular gyrus gray matter volume (GMV) was positively related to proficiency C_LIO_LIGMV was positively related to balance, but not after controlling for proficiency C_LIO_LIRelations with these language dimensions are located outside of language cortex C_LIO_LINo significant associations were observed for cortical thickness C_LI

Language experience is a powerful driver of neurocognitive plasticity, shown to modulate attentional and executive processing in speakers of multiple languages. This paper investigated how immersion in a second-language environment shapes attentional processing of speech. Fifty-eight bilingual Chinese-English speakers matched on their English language proficiency listened to competing continuous speech streams in a naturalistic listening task. They were immersed either in their native language environment (Beijing, China), or in the second language environment (Cambridge, UK). In an identical EEG experiment across the two immersion contexts, we assessed the listeners cortical tracking of attended and unattended speech and task-related attentional allocation using Temporal Response Function (mTRF) and Power Spectral Density (PSD) analyses. Behavioral comprehension of the attended narratives was uniformly high. PSD analyses showed no group difference in task-related attentional allocation, but mTRF results revealed robust differences in cortical tracking, with increased tracking of attended - but not unattended - streams in the immersed group, driven by the delta band (1-4 Hz). This boost in tracking of the attended signal declined with prolonged immersion, indicative of changes to attentional speech processing as the language environment stabilizes and consistent with the expansion-renormalization framework of neurocognitive adaptation. Jointly, these data imply that immersion in second-language environments shapes the way listeners encode speech, sharpening the brains ability to extract target auditory information from background noise. They furthermore suggest that, rather than being static or monotonous, this modulation reflects a flexible and dynamic process that is continuously shaped by changes in environmental demands and their duration. Key pointsO_LISecond language immersion boosts cortical tracking of attended speech, driven by the delta band (1-4 Hz). C_LIO_LIThis boost decreases with prolonged immersion, reflecting the dynamic, expansion-renormalization adaptation trajectory. C_LIO_LIImmersion does not influence task-related attentional allocation. C_LI

A network of left frontal and temporal brain regions supports high-level language processing-- including the processing of word meanings, as well as word-combinatorial processing--across presentation modalities. This core language network has been argued to store our knowledge of words and constructions as well as constraints on how those combine to form sentences. However, our linguistic knowledge additionally includes information about sounds (phonemes) and how they combine to form clusters, syllables, and words. Is this knowledge of phoneme combinatorics also represented in these language regions? Across five fMRI experiments, we investigated the sensitivity of high-level language processing brain regions to sub-lexical linguistic sound patterns by examining responses to diverse nonwords--sequences of sounds/letters that do not constitute real words (e.g., punes, silory, flope). We establish robust responses in the language network to visually (Experiment 1a, n=605) and auditorily (Experiments 1b, n=12, and 1c, n=13) presented nonwords relative to baseline. In Experiment 2 (n=16), we find stronger responses to nonwords that obey the phoneme-combinatorial constraints of English. Finally, in Experiment 3 (n=14) and a post-hoc analysis of Experiment 2, we provide suggestive evidence that the responses in Experiments 1 and 2 are not due to the activation of real words that share some phonology with the nonwords. The results suggest that knowledge of phoneme combinatorics and representations of sub-lexical linguistic sound patterns are stored within the same fronto-temporal network that stores higher-level linguistic knowledge and supports word and sentence comprehension.

Ergativity marks subject arguments as agents of a transitive event and thereby signals verbal transitivity and influences language comprehension. We report here on an event-related brain potentials (ERP) study in Hindi, in which we investigated this interconnection to ascertain whether the ergative case as a processing cue and its ERP correlates can be generalized across and within ergative languages. The case marking on the subject argument (ergative or nominative case) in our study either matched or mismatched with the transitivity of the light verb (transitive or intransitive) in compound light verb constructions. Ergative case violations due to an intransitive light verb evoked an N400 effect, whereas nominative case violations due to a transitive light verb elicited a P600 effect. The results reveal neurophysiological differences in the processing of ergative and nominative case alignment modulated by the transitivity of the light verbs. The findings highlight the need for cross-linguistic research to aim beyond universality and elucidate the mechanism underlying the processing of language-specific structural variations.

This neuroimaging study investigated the neural infrastructure of sentence-level language production. We compared brain activation patterns, as measured with BOLD-fMRI, during production of sentences which differed in verb argument structures (intransitives, transitives, ditransitives) and the lexical status of the verb (known verbs or pseudo-verbs). An example for the type of sentence to be produced started a mini-block of six sentences with the same structure. For each trial, participants were first given the (pseudo-)verb followed by three geometric shapes to serve as verb arguments in the sentences. Production of sentences with known verbs yielded greater activation compared to those with pseudo-verbs in the core language network of left inferior frontal gyrus, the left posterior middle temporal gyrus, and a more posterior middle temporal region extending into the angular gyrus (LpMTG/AG), analogous to effects observed in language comprehension. Increasing the number of verb arguments led to greater activation in an overlapping left pMTG/AG area, particularly for known verbs, as well as in the bilateral precuneus. Thus, producing sentences with more complex structures using existing verbs lead to increased activation in the language network, suggesting some reliance on memory retrieval of stored lexical-syntactic information during sentence production. This study thus provides evidence from sentence-level language production in line with functional models of the language network that have so far been mainly based on single word production, comprehension and processing in aphasia.

French accentuation is held to belong to the level of the phrase. Consequently French is considered a language without accent with speakers that are deaf to stress. Recent ERP-studies investigating the French initial accent (IA) however demonstrate listeners to not only discriminate between different stress patterns, but also expect words to be marked with IA early in the process of speech comprehension. Still, as words were presented in isolation, it remains unclear whether the preference applied to the lexical or to the phrasal level. In the current ERP-study, we address this ambiguity and manipulate IA on words embedded in a sentence. Furthermore, we orthogonally manipulate semantic congruity to investigate the interplay between accentuation and later speech processing stages. Results reveal an early fronto-centrally located negative deflection when words are presented without IA, indicating a general dispreference for words presented without IA. Additionally, we found an effect of semantic congruity in the centro-parietal region (the traditional region for N400), which was bigger for words without IA than for words with IA. Furthermore, we observed an interaction between metrical structure and semantic congruity such that {+/-}IA continued to modulate N400 amplitude fronto-centrally, but only in the sentences that were semantically incongruent. The results indicate that presenting word without initial accent hinders semantic conflict resolution. This interpretation is supported by the behavioral data which show that participants were slower and made more errors words had been presented without IA. As participants attended to the semantic content of the sentences, the finding underlines the automaticity of stress processing and indicates that IA may be encoded at a lexical level where it facilitates semantic processing.

When bilinguals frequently switch between their first (L1) and second (L2) languages during speech production, we usually observe two phenomena: (i) language switch cost, where switching to a different language is more difficult than staying in the same one, and (ii) reversed language dominance, where L1 production becomes slower than L2 production. These effects are thought to reflect language control mechanisms, yet the underlying neural bases remain debated. In this study, we addressed this question by using the precision functional magnetic resonance imaging (fMRI) based on functional localization. Forty-one Polish-English bilinguals performed a language switching task (LST), in which they named pictures in L1 or L2 based on color cues. We investigated mechanisms behind two indices of language control commonly observed in the LST. First, we asked whether the domain-general resources supporting language switch cost overlap with nonverbal task switch cost. Second, we asked whether reversed language dominance reflects changes in language activation in the language-specific system, or whether it is related to increased engagement of domain-general control mechanisms. Results indicated that the language switch cost and nonverbal task switch cost share overlapping domain-general neural mechanisms. Similar to the language switch cost, reversed language dominance primarily engages domain-general processes rather than language-specific resources. HighlightsO_LIfMRI combined with functional localization approach is implemented to examine the neural mechanisms underlying language switch cost and reversed language dominance. C_LIO_LILanguage switch cost relies on neural mechanisms shared with nonverbal switch cost within the Multiple Demand network. C_LIO_LIReversed language dominance is primarily supported by the domain-general rather than the language-specific mechanisms. C_LIO_LIDomain-general neural mechanisms play a pivotal role in bilingual language switching in speech production. C_LI

Language processing is supported by distributed neural systems. Yet most research examines these systems at the population-average level, obscuring how individual cognitive differences shape language-related brain activity. In this study, we combined comprehensive cognitive assessments and task-based fMRI in a large sample of healthy adults (N = 205) to examine how variability in linguistic knowledge, working memory, processing speed, and non-verbal reasoning influenced neural responses in four language tasks: lexical decision, picture naming, sentence comprehension, and sentence production. All tasks engaged canonical left-lateralized language regions. However, individual differences in cognitive skills were not associated with modulations within commonly activated regions, but rather with modulations in domain-general systems outside traditional perisylvian language areas, mainly the default mode and dorsal attention networks. Notably, activations in these domain-general regions were predominantly negatively correlated with cognitive skills, indicating that individuals with lower cognitive skills draw on these broader neural resources more than higher-skilled individuals, possibly as a compensatory mechanism. These results reveal that while canonical language regions are consistently engaged during language tasks, the recruitment of domain-general systems acts as a variable resource modulated by individuals cognitive skills. Overall, our findings demonstrate that individual cognitive profiles determine how distributed brain systems are dynamically engaged to scaffold language processing.

Prior studies have reported inconsistent results for neuroanatomical differences between early bilinguals and monolinguals. These studies primarily measured gray matter volume (GMV), involved small samples, and prioritized adults. Few studies of early bilinguals have measured cortical thickness (CT), which offers more anatomical specificity. It remains unclear whether results derived from differing metrics and approaches (e.g., vertex-versus parcel-wise analyses) converge. Using data from the Adolescent Brain Cognitive DevelopmentSM (ABCD) Study, we compared neuroanatomy between large groups of early cultural Spanish-English bilingual and English monolingual children (N = 1,209) matched on age, pubertal status, sex, handedness, socioeconomic status (SES), and nonverbal reasoning. Whole-brain voxel-based morphometry revealed areas of greater and of lesser GMV in bilinguals than monolinguals across all lobes. Vertex-wise CT analyses similarly identified widespread differences, with bilinguals showing areas of both thicker and thinner cortex. We contextualized these findings with parcel-wise CT analyses (average CT values), utilizing two atlases of differing spatial granularity. Parcel-wise results showed good correspondence with vertex-wise findings when implementing the more fine-grained atlas (Destrieux), but use of the coarser atlas (Desikan-Killiany) provided results that led to different conclusions. Finally, we tested for interaction effects between bilingualism and SES on CT and found several regions where differences between bilinguals and monolinguals in CT were modulated by SES. Together, these findings indicate that early bilingualism is associated with extensive neuroanatomical differences relative to monolinguals during childhood, and that these results can vary as a function of neuroanatomical metric, analysis approach, atlas granularity, and SES. Research HighlightsEarly Spanish-English bilingual and monolingual children differ in gray matter volume and cortical thickness across multiple brain regions. Cortical thickness differences between bilinguals and monolinguals cannot be firmly attributed to adaptations associated with language or executive control. Socioeconomic status modulates cortical differences between early bilinguals and monolinguals, revealing unique thickness patterns for those with lower versus higher SES backgrounds. Parcel-wise between-group cortical thickness results are affected by atlas choice and can influence the interpretation of the findings.

A central question in psycholinguistics in visual word recognition is whether morphologically complex words are obligatorily decomposed into stems and affixes during visual word recognition or whether whole- word access can occur when forms are frequent and familiar. The present study investigated how morphological complexity and lexical frequency jointly shape neural responses by leveraging Korean nominal inflection, whose transparent stem-suffix structure permits a clean dissociation between base (stem) frequency and surface (whole- word) frequency. Twenty-five native Korean speakers completed a rapid event-related fMRI lexical decision task involving simple and inflected nouns that varied parametrically in both frequency measures. Representational similarity analysis (RSA) revealed robust encoding of surface frequency--but not base frequency--in the inferior frontal gyrus (IFG) pars opercularis and supramarginal gyrus (SMG), with significantly stronger correlations for inflected than simple nouns. Univariate analyses converged with this result: surface frequency selectively increased activation for inflected nouns in inferior parietal regions, whereas base frequency showed no reliable effects in any ROI. These findings challenge models positing obligatory pre-lexical decomposition, instead supporting accounts in which morphological processing is shaped by post-lexical, usage-driven lexical statistics. Taken together, our findings shed light on a distributed perspective on morphological processing, suggesting that structural and statistical factors jointly constrain access to morphologically complex forms.

Speech is a complex and ambiguous acoustic signal that varies significantly within and across speakers. A prevalent and ubiquitous example of such variation is accented speech, to which humans adapt extremely rapidly. The goal of this study is to uncover the neurobiological bases of the attunement process that enables such fluent comprehension. Twenty-four native English participants listened to words spoken by an unaccented "canonical" American talker and two "accented" talkers, and performed a word-picture matching task, while magnetoencephalography (MEG) was recorded. Accented speech was created by including systematic phonological substitutions within the word (e.g. [s] [->] [sh]). Activity in the auditory cortex (superior temporal gyrus) was greater for accented speech, but, critically, this was not attenuated by exposure. By contrast, prefrontal regions showed an interaction between the presence of an accent and amount of exposure: while activity decreased for canonical speech over time, responses to accented speech remained consistently elevated. Grainger causality analyses further revealed that prefrontal responses serve to modulate activity in auditory regions, suggesting the recruitment of top-down processing to decode accented signal. In sum, our results show that accented speech does not elicit the same prefrontal reduction in amplitude over time that unaccented speech does, and points to a dynamic exchange of information between the prefrontal and auditory cortices in order to recalculate phonetic classification and subsequent identification of lexical items. Significance statementHuman ability to adapt to different peoples idiosyncratic pronunciations is a hallmark of speech comprehension. This study aims to address whether adaptation to speakers accents manifests itself at the perceptual level (i.e. through adaptation of low-level neural responses in the auditory cortex) or at the post-perceptual level (i.e. higher-order regions correcting the sensory signal received from auditory cortex). Our results support the post-perceptual hypothesis: we found that responses in auditory cortex emitted an error-like signal that was invariant to exposure; whereas responses in the prefrontal cortex were modulated by exposure. These findings provide initial insight into accent adaptation, and illuminate the computational stages supporting speech comprehension more generally.

The extent to which the language production and comprehension systems overlap remains debated. We address this debate using a dataset where participants engaged in unscripted conversations, while scanned with fMRI. Word predictability was hypothesized to rely on different processes, depending on whether the word was uttered or heard. We employed the information-theoretic measure of surprisal (the negative log probability of a word occurring, given the preceding context) as a parametric modulator, controlling for the words overall frequency. The results for production surprisal revealed activation in the left superior and inferior frontal gyri and motor areas. A large bilateral cluster in the posterior part of the medial prefrontal cortex extended from the supplementary motor area to the anterior cingulate cortex. The results for comprehension surprisal replicated findings from non-conversational contexts, showing involvement of the bilateral superior temporal gyrus/sulcus, presumably supporting bottom-up processes for prediction error detection. Importantly, no overlap in the neural infrastructure of production and comprehension was observed, suggesting that word predictability processes in production and comprehension differ. We suggest that while the comprehension system handles prediction errors, the production system minimizes these errors through adaptation, all to achieve successful communication.