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Invited Symposium 3 - Neuroplasticity of Language: Insights from Exceptional Language Experience.

Tuesday, March 23, 10:00 am – 12:00 pm, Salons A-E

Chairs: David Corina¹ (dpcorina@ucdavis.edu) & Marina Bedny² (marina.bedny@jhu.edu); ¹University of California Davis, ²Johns Hopkins University
Presenters: Saima Malik Moraleda, Marina Bedny, Patrick C. Trettenbrein, Nadine Gaab

Advances in cognitive neuroscience have yielded broad agreement that multiple distinct cortical networks are involved in language processing, including the frontotemporal, language network, a domain-general frontoparietal multiple-demand network and specialized peripheral input and output systems (e.g., visual word form area.) However, existing models rest largely on evidence from monolingual and bilingual speakers of aural languages that does not capture the breadth of human language experience. How do existing accounts apply to language processing across modalities, markedly different linguistic and sensory experiences? This symposium explores robustness and plasticity of language neurobiology across populations with varying language and sensory experience. Dr. Saima Malik Moraleda examines the contributions of language-specific and domain-general networks in polyglots—individuals with high proficiency in five or more spoken languages. Dr. Patrick Trettenbrein and Dr. Marina Bedny examine the brain networks supporting language processing in Deaf users of signed languages with varying ages of language experience. Dr. Nadine Gaab investigates the development of language networks through longitudinal behavioral and neuroimaging studies of children who become successful readers and those who experience reading difficulties. Together, these perspectives inform current models of human language as they apply to populations with varying linguistic experience, sensory experience, and language modality. By examining both continuity and plasticity across these populations, the symposium aims to clarify the functional specializations and adaptive capacities of the brain networks that support language.

Presentations

Talk 1 - Proficiency-driven recruitment of the language network: Insights from polyglots and heritage speakers

Saima Malik Moraleda¹; ¹Massachusetts Institute of Technology

What determines how strongly distinct brain networks respond to a language? We investigate how the frontotemporal domain-specific language network (Fedorenko et al., 2011) and the fronto-parietal domain-general Multiple Demand network (Duncan, 2010) are recruited as a function of language experience, using precision fMRI across two populations: polyglots and heritage speakers. In the first study (Malik-Moraleda, Jouravlev et al., 2023), we characterized the language and MD networks in 34 polyglots, including 16 hyperpolyglots with knowledge of ten or more languages. Participants listened to their native language, three non-native languages of varying proficiency, related unfamiliar languages, and unfamiliar unrelated languages. Response magnitude across the language network scaled with proficiency: higher-proficiency languages drove stronger network engagement. Alongside this, lower-proficiency and unfamiliar languages engaged the Multiple Demand network, associated with effortful processing. We replicate the finding that polyglots show attenuated responses to their native language relative to non-polyglots (Jouravlev et al., 2021), consistent with experience-driven neural efficiency. In the second study, using the precision fMRI approach, we tested heritage speakers: individuals who acquired a language early in life but subsequently lost proficiency. Heritage speakers showed reduced language network engagement when listening to stories in their heritage language, scaling with comprehension scores for the passages measured outside the scanner, and engagement of the Multiple Demand network that was absent in their dominant language. These results suggest that, regardless of when a language is acquired, language network engagement reflects the ease with which the brain performs core linguistic computations, while reduced proficiency draws on domain-general resources.

Talk 2 - Insights into language modality and experience from precision fMRI and MVPA with d/Deaf signers of ASL

Marina Bedny¹; ¹Johns Hopkins University.

What aspects of language neurobiology are modality specific (i.e., specific to spoken vs signed/visual modalities), and which are modality invariant? How does age of language experience influence language neurobiology? Most d/Deaf children are born to hearing families and many experience varying degrees of delayed access to a visuomanual sign language. Such delays are associated with long-term behavioral differences, including reduced mastery of phonology and grammar. I will discuss insights from precision fMRI and multivoxel pattern analysis into language domain specificity in d/Deaf signers with varying ages of exposure to American Sign Language. In spoken languages, fronto-temporal language systems are domain specific and functionally distinct from domain general working memory systems and from visual semantics. For instance, the representations of action verbs are in part anatomically dissociable from representations of visual actions. We show that in d/Deaf signers, the frontotemporal language system is domain specific and distinct from domain general working memory systems. In ASL, ‘iconic’ action verbs (e.g., give, open) perceptually resemble the actions they refer to. Nevertheless, their meaning is decoded from language-specific neural populations in posterior temporal networks that are distinct from neural populations encoding meaning-matched action videos. This language-specific pattern holds even in late learners of ASL. Fronto-temporal systems show a high degree of domain specificity for sign and spoken languages, even with delayed access. However, late learners show enhanced recruitment of domain-general working memory systems during language processing, suggesting less efficiency. Recruitment of domain general working memory systems may be a signature of late language access.

Talk 3 - The Language Network Beyond Speech: Universality and Plasticity in Deaf Signers

Patrick C. Trettenbrein¹; ¹University of Göttingen, Germany.

Deafness and sign languages provide a stringent test of whether or to what extent the brain’s language system is tied to speech or constitutes a modality-independent neural architecture. Converging evidence from neuroimaging meta-analyses, task-based fMRI and diffusion MRI supports a primarily left-hemispheric fronto-temporal language network that is implicated in integrating words or signs into sentences across sign language, speech, as well as written language comprehension. The principal white-matter pathways connecting this functional network do not differ detectably between deaf signers and hearing non-signers. These findings indicate that the brain’s core language network develops independently of auditory experience. However, diffusion MRI also reveals macro- and micro-structural alterations primarily in right-hemispheric temporal, frontal, and parietal pathways, potentially reflecting the visuospatial and attentional demands of sign language. In contrast, an analysis of T1-weighted scans from the same participants failed to replicate structural group differences frequently reported in the literature, underscoring the limited power and reproducibility of small-sample comparisons. Preliminary structural and resting-state MRI analyses from a large multisite sample provide a broader test of these effects: Morphometric and connectivity-gradient analyses suggest substantial preservation of macro-scale cortical organisation alongside selective changes in auditory cortex and its functional embedding within attention and control systems. Together, these findings support the notion of a modality-independent core network for language that flexibly interfaces with modality-specific systems depending on the modality of language use.

Talk 4 - The Reading Brain from Womb to Classroom: Typical and Atypical Development, Neuroplasticity, and Implications for a Preventative Education Model

Nadine Gaab¹; ¹Harvard University

Learning trajectories are shaped by the dynamic interplay between nature and nurture, starting in utero and continuing throughout the lifespan. Learning differences/disabilities are often not identified until childhood or adolescence, but divergent trajectories of brain development may be present as early as the prenatal period. Furthermore, children's experiences and their interactions with their environment have long-lasting influences on cognitive development, neuroplasticity, and future academic outcomes. This talk will focus on learning differences in reading acquisition within a learning disability framework. It will present results from our longitudinal behavioral and neuroimaging studies that characterize differences in learning to read as a complex outcome of cumulative risk and protective factors interacting within and across genetic, neurobiological, cognitive, and environmental levels from infancy to adulthood. Results are discussed within an early multifactorial framework of learning differences, emphasizing screening in educational and community settings, early identification, preventative strategies, and a research-to-practice tool development pipeline. Finally, using a global lens, the implications of these findings for contemporary challenges in educational, clinical, and policy practice are discussed.