Neurobiology of Language最新文献

Speech development requires precise timing and sensorimotor integration, supported by neural oscillations that synchronize activity across auditory, motor, and cognitive circuits. Among speech-relevant frequency bands, beta oscillations (13-30 Hz) are critical for timing and coordination, supporting sensorimotor processing and speech preparation. Beta desynchronization (power decreases) is typically observed prior to movement, reflecting motor planning, and beta activity also supports cognitive functions such as attention and anticipation. Although age-related changes in beta power have been documented, its developmental trajectory during speech processing remains underexplored. Here, we compared beta power dynamics in 28 adults (mean age = 27.8 yr) and 50 children (mean age = 10.3 yr) during speech perception and production tasks using EEG. On each trial, participants received a visual cue indicating the condition ("Say," "Hear," or "See"), followed by rhythmic tones and a warning cue presented as a picture with its name (e.g., cat) in Say and Hear, but only as a picture in See. A Go cue then prompted participants to speak, listen, or maintain fixation. Beta power was analyzed in three time windows: postwarning cue (P1), pre-Go cue (P2), and post-Go cue (P3). Adults exhibited significant beta power decreases across all time windows, particularly in Say, indicating mature sensorimotor and cognitive integration. In contrast, children showed no significant condition effects and minimal beta reduction in P3. Beta modulation was negatively correlated with age in children, suggesting ongoing maturation of beta oscillations. These findings highlight key developmental differences in beta oscillations relevant to speech processing.

Successful coordination of the functional networks underlying reading is highly dependent on the underlying white matter tracts that connect these regions. Continuous theta burst stimulation (cTBS) can temporarily inhibit brain activity in targeted brain networks and has been shown to modulate reading ability. It was hypothesized that measures of diffusivity would predict change in reading efficiency following stimulation to the left temporal-parietal junction (TPJ), a targeted node of the dorsal stream of the reading network. Fifty-three adults between the ages of 18 and 50 years (M = 22.79, SD = 5.40; 34 female) with a range in reading ability completed sight word and pseudoword fluency measures prior to and immediately following cTBS to either the left or right TPJ or a control site. Participants also completed an MRI session including anatomical and diffusion weighted imaging sequences. Regression analyses were conducted to predict change in reading fluency following cTBS. Tracts associated with the reading network including the arcuate fasciculus, inferior longitudinal fasciculus, and portions of the superior longitudinal fasciculus, as well as the corpus callosum significantly predicted reliable change in a test of word reading efficiency-sight word efficiency subtest following stimulation of the left TPJ. These findings suggest that increased diffusivity of white matter tracts associated with the left hemisphere reading network and their right hemisphere homologues may support the impact of cTBS following stimulation to a targeted node of the reading network. Individual differences in white matter diffusivity may underlie differences in behavioral outcomes following neuromodulation.

Public speaking is a fundamental form of communication across a wide range of domains; however, the neural mechanisms underlying audience engagement during different speeches remain poorly understood. In particular, it is unclear which functional brain networks support the dynamic fluctuations of audience engagement and what neurobiological processes underlie these effects. In this study, we used naturalistic fMRI combined with intersubject correlation (ISC) analysis to examine how carefully selected and matched speeches, with varying levels of audience engagement, influence neural activity. Our results revealed that the more engaging speech elicited significantly greater interbrain neural synchronization, as indexed by ISC, across a broad range of brain regions. Notably, these engagement-related effects were most prominent in networks associated with language processing and theory of mind, highlighting their critical roles in facilitating shared audience experiences during compelling public communication. A sliding-window analysis further revealed substantial temporal fluctuations in interbrain synchronization throughout the speech. Additionally, neurobiological annotation analyses identified strong associations between engagement-related ISC effects and molecular pathways involved in trans-synaptic signaling, suggesting that intrabrain neuronal communication may contribute to modulating interbrain synchronization. By integrating naturalistic fMRI with ISC analyses, this study offers a promising framework for investigating dynamic neural synchronization among audience members. These findings have broad implications for fields such as education and leadership development, where a deeper understanding of the neural basis of audience engagement could inform strategies to enhance public speaking and communication effectiveness.

Oral reading relies on lexical and sublexical processes with distinct neural mechanisms. Damage within the sublexical system causes phonological alexia, a blanket diagnosis describing acquired deficits in reading unfamiliar words. Improving the precision of alexia diagnosis requires understanding the neurocognitive basis of specific reading subprocesses. This study investigated the neural correlates of sublexical reading in 64 adults with chronic left-hemisphere stroke (LHS), focusing on lesions that impair the use of learned orthography-to-phonology (OP) mappings to read new words. Participants read aloud real words and three types of pseudowords varying in the number of plausible OP mappings at the level of the orthographic body: zero mappings (0M), one mapping (1M), and multiple mappings (MM). LHS participants exhibited phonological reading deficits with an exaggerated lexicality effect compared to 71 neurotypical controls. Across both groups, pseudowords with learned OP mappings were read more accurately than those without. Voxelwise and connectome-based lesion-symptom mapping revealed that relative lexical reading deficits were associated with lateral temporal lesions, while sublexical reading deficits were associated with lesions or disconnections of the left inferior frontal (IFG), supramarginal, and pre/postcentral gyri. Applying learned OP mappings relied on anterior IFG and frontoparietal connections, while resolving multiple plausible OP mappings relied on intraparietal connections. These results underscore the role of learned mutigraphemic OP mappings in sublexical reading, and demonstrate that disruptions of different sublexical reading subprocesses result in subtly different deficit patterns. Dissecting the neurocognitive basis of reading subprocesses may improve the precision of alexia diagnosis and point to new treatments.

Learning to recognize and produce foreign speech sounds can be challenging, particularly when only subtle differences distinguish these new sounds from phonemes in the native language. Functional neuroimaging evidence shows that the motor cortex is involved in speech production and in perceptual phonemic processing. This highlights the embodied nature of speech perception, predicting the potential benefits of sensorimotor-based training approaches to enhance the acquisition of foreign speech sounds. Hence, here we first review current findings on the motor contribution to not only native but also non-native phoneme perception. Available evidence has established that motor cortical activity especially shows up under non-optimal perceptual conditions, such as when native phonemes are degraded by noise or when listeners perceive non-native speech sounds. Drawing upon this evidence, we then review training paradigms that have been developed for learning foreign phonemes, with a special emphasis on those embedding manual gestures as cues to represent phonetic features of the to-be-learned speech sounds. By pointing to both strengths and caveats of available studies, this review allows to delineate a clear framework and opens perspectives to optimize foreign phoneme learning, and ultimately support perception and production.

As the auditory brain becomes functional during the third trimester of pregnancy, both biological and environmental processes begin shaping its maturation, influencing how speech sounds are perceived. Biological factors, such as sex, introduce early genetic differences, while environmental experiences, like bilingualism, modulate the auditory input that infants receive. Although existing research highlights the impact of sex and bilingualism on the development of speech perception, the neural mechanisms remain unclear. In this study, we recorded frequency-following responses longitudinally, at birth, 6 months, and 12 months of age in 73 infants exposed to varying degrees of bilingual input. We modeled the developmental trajectories for neural encoding of voice pitch and speech formant structure, finding significant maturation during the first 6 months, followed by less pronounced change through the first year. Distinct developmental patterns emerged as a function of sex and bilingualism, revealing their influence on neural attunement to key speech-sound features. Female infants exhibited stronger neural encoding of both pitch and formant structure, depicting a distinctive quadratic trajectory that peaked at 6 months. Bilingual exposure notably predicted lower neural pitch encoding values at 6 months, but higher values by 12 months. A positive effect of bilingualism on speech formant encoding was observed throughout the first year. These findings reveal how biological and environmental factors contribute to individual variability in early auditory development and speech acquisition.

Age-related declines in cognitive function are often accompanied by changes in brain activity and network organization. This study investigated the relationship between resting state brain activity and age-related differences in speech production. We hypothesized that older adults would exhibit altered functional connectivity and activation intensity, correlating with reduced speech quality. Resting state functional MRI data were collected and a composite measure of speech complexity and fluency was calculated from younger and older adults. Results revealed significantly worse speech performance in older adults, accompanied by less segregated whole-brain networks, reduced amplitude of low-frequency fluctuations, and more heterogeneous brain states. Univariate regression analyses indicated stronger brain-behavior relationships in younger adults, while multivariate regression analyses revealed that age-related differences in resting state brain state patterns critically relate to speech production differences. Notably, the language network remained relatively stable with age, whereas whole-brain status became very important for speech performance in older adults. These findings suggest that resting state brain activity, particularly whole brain network characteristics, may serve as a stable biomarker of age-related changes in speech production.

Developmental stuttering is a complex neurodevelopmental condition associated with structural and functional anomalies in the basal ganglia-thalamo-cortical (BGTC) circuits that support speech planning and execution. In this study, we examined hypothesized impairments in the planning and motor circuits of the speech network in children who stutter (CWS), compared to children who do not stutter (CNS), using person-specific functional connectivity maps derived from resting-state functional magnetic resonance imaging (rsfMRI) data. RsfMRI data were acquired from 73 CWS and 74 CNS, aged 3 to 10 years. Twelve regions of interest within the speech motor networks were extracted. Functional connectivity was assessed using confirmatory subgrouping group iterative multiple model estimation (CS-GIMME), which estimates group-, subgroup-, and individual-level connections. Subgroup-level functional connectivity patterns revealed altered connections among CWS in both planning and motor loops, including reduced within-network connectivity, compared to CNS. CWS showed connectivity between the left posterior inferior frontal sulcus and left ventral lateral thalamus that was not observed in CNS. Furthermore, centrality of the left ventral lateral thalamus and right ventral premotor cortex were increased in CWS relative to CNS. Significant differences between CWS and CNS in within-network connectivity highlight early developmental alterations that affect the BGTC circuitry, pointing toward inefficiencies in the neural network that supports the programming, planning and timing of speech motor sequences.

The ability to read relies on the rapid mapping of perceived visual letters and their combinations (i.e., visual word forms) to phonology and meaning. The central role of the left ventral occipito-temporal cortex (VOTC) in processing letter strings, initially suggested by lesion studies, is now widely accepted. Although this brain region has been extensively studied with functional magnetic resonance imaging (fMRI), its causal role as a critical node of a cortical network for reading remains unclear. Here we report a comprehensive case of pure alexia during direct electrical stimulation (DES) of the left VOTC (patient SV, female, 38 yr old, implanted with intracerebral electrodes for refractory epilepsy). During DES of the left posterior occipito-temporal sulcus, but not of neighboring and remote cortical sites, SV was transiently impaired at reading single words while being able to slowly read letter-by-letter. However, SV was impaired when presenting a single letter in a rapid serial visual presentation, which showed that their letter reading is not entirely preserved. In contrast, DES to the same critical sites left performance for oral naming, auditory naming, reading numbers, writing, auditory lexical decision, and semantic matching of pictures unaffected. Intracerebral electrophysiological frequency-tagging investigations showed highly word-selective neural responses at the critical sites. These functional responses were abolished by concurrent DES, which also affected remote word-selective neural activity in the left VOTC. Altogether, these observations provide original evidence for word-selective representations of the left VOTC as a critical node of the cortical reading network.

Recovery of language function in post-stroke aphasia is affected by many variables, including aphasia severity, age, lesion site and size, and brain health. Semantic and phonological therapies are often used to target naming abilities, and when successful their benefits can extend to discourse production, which has emerged as a promising task to evaluate language processing and recovery in aphasia. Here, after characterizing the lesion and white matter integrity predictors for discourse production before treatment, we asked whether brain integrity at baseline is predictive of treatment generalization to discourse. In a large sample of participants with chronic aphasia (N = 88), we ran region-based lesion-symptom mapping on discourse measures (including fluency, sentence processing abilities, and error types) at baseline, on discourse changes following phonological and semantic treatment separately, and at 1 month and 6 months post-treatment. Discourse productivity at baseline was associated with the integrity of regions and white matter tracts in the dorsal stream. Lesions in the hippocampal system and cortical temporal regions were associated with less improvement in discourse following both phonological and semantic treatment. Long-term improvement was instead predicted by the integrity of the fornix and temporal cortical regions, suggesting that while the hippocampal system is important for learning, learned functions rely on connectivity with cortical areas. The results suggest that the generalization of word-level treatment to discourse production is facilitated by an intact hippocampal system in the medial temporal lobe.