{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T20:07:06Z","timestamp":1789589226578,"version":"build-2803163510"},"reference-count":65,"publisher":"MIT Press","license":[{"start":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T00:00:00Z","timestamp":1783555200000},"content-version":"vor","delay-in-days":189,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["direct.mit.edu"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2026,9,4]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>When humans and large language models (LLMs) process the same text, activations in the LLMs correlate with brain activity measured, e.g., using functional magnetic resonance imaging (fMRI). Moreover, it has been shown that, as the training of an LLM progresses, the performance in predicting brain activity from its internal activations improves more in the left hemisphere than in the right one. The aim of the present work is to understand which kind of competence acquired by the LLMs underlies the emergence of this left-right asymmetry. Using the OLMo-2 7B language model at various training checkpoints and fMRI data from English participants, we compare the evolution of the left-right asymmetry in the correlation between brain activity and model predictions alongside performance on several benchmarks. We observe that the asymmetry co-emerges with the formal linguistic abilities of the LLM. These abilities are demonstrated in two ways: by the model\u2019s capacity to assign a higher probability to an acceptable sentence than to a grammatically unacceptable one within a minimal contrasting pair, and by its ability to produce well-formed text. By contrast, the left-right asymmetry does not align with the performance on arithmetic or Dyck language tasks; nor with text-based tasks involving world knowledge and reasoning. We generalize these results to another family of LLMs (Pythia) and two other languages, French and Chinese. Our observations indicate that the left-right asymmetry in brain predictivity matches the progress in formal linguistic competence.<\/jats:p>","DOI":"10.1162\/nol.a.284","type":"journal-article","created":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T19:38:37Z","timestamp":1783625917000},"update-policy":"https:\/\/doi.org\/10.1162\/mitpressjournals.corrections.policy","source":"Crossref","is-referenced-by-count":0,"title":["Left-Right Asymmetry in Predicting Brain Activity From LLMs\u2019 Representations Emerges With Their Formal Linguistic Competence"],"prefix":"10.1162","volume":"7","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2936-2780","authenticated-orcid":true,"given":"Laurent","family":"Bonnasse-Gahot","sequence":"first","affiliation":[{"name":"Centre d\u2019Analyse et de Math\u00e9matique Sociales, CNRS, EHESS, Paris, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3324-666X","authenticated-orcid":true,"given":"Christophe","family":"Pallier","sequence":"additional","affiliation":[{"name":"Cognitive Neuroimaging Unit, CNRS, INSERM, CEA, Neurospin Center, Gif-sur-Yvette, France"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"281","published-online":{"date-parts":[[2026,9,4]]},"reference":[{"key":"2026091615504241800_bib1","doi-asserted-by":"publisher","first-page":"24321","DOI":"10.18653\/v1\/2025.emnlp-main.1237","article-title":"From language to cognition: How LLMs outgrow the human language network","volume-title":"Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing","author":"AlKhamissi","year":"2025"},{"key":"2026091615504241800_bib2","doi-asserted-by":"crossref","first-page":"21895","DOI":"10.52202\/075280-0958","article-title":"Scaling laws for language encoding models in fMRI","volume":"36","author":"Antonello","year":"2023","journal-title":"Advances in Neural Information Processing Systems"},{"key":"2026091615504241800_bib3","first-page":"2397","article-title":"Pythia: A suite for analyzing large language models across training and scaling","volume-title":"Proceedings of the 40th International Conference on Machine Learning","author":"Biderman","year":"2023"},{"issue":"4","key":"2026091615504241800_bib4","doi-asserted-by":"publisher","first-page":"978","DOI":"10.1212\/WNL.46.4.978","article-title":"Determination of language dominance using functional MRI: A comparison with the Wada test","volume":"46","author":"Binder","year":"1996","journal-title":"Neurology"},{"key":"2026091615504241800_bib5","volume-title":"Natural language processing with Python: Analyzing text with the Natural Language Toolkit","author":"Bird","year":"2009"},{"key":"2026091615504241800_bib6","first-page":"125231","article-title":"fMRI predictors based on language models of increasing complexity recover brain left lateralization","volume-title":"Proceedings of the 38th International Conference on Neural Information Processing Systems","author":"Bonnasse-Gahot","year":"2024"},{"key":"2026091615504241800_bib7","doi-asserted-by":"publisher","first-page":"e3929","DOI":"10.7717\/peerj.3929","article-title":"Measuring language lateralisation with different language tasks: A systematic review","volume":"5","author":"Bradshaw","year":"2017","journal-title":"PeerJ"},{"issue":"1","key":"2026091615504241800_bib8","doi-asserted-by":"publisher","first-page":"377","DOI":"10.3406\/bmsap.1865.9495","article-title":"Sur le si\u00e8ge de la facult\u00e9 du langage articul\u00e9","volume":"6","author":"Broca","year":"1865","journal-title":"Bulletins et M\u00e9moires de la Soci\u00e9t\u00e9 d\u2019Anthropologie de Paris"},{"issue":"8","key":"2026091615504241800_bib9","doi-asserted-by":"publisher","first-page":"1504","DOI":"10.1016\/j.neuron.2025.12.030","article-title":"The cerebellar components of the human language network","volume":"114","author":"Casto","year":"2026","journal-title":"Neuron"},{"key":"2026091615504241800_bib10","first-page":"1336","article-title":"Disentangling syntax and semantics in the brain with deep networks","volume-title":"Proceedings of the 38th Interational Conference on Machine Learning","author":"Caucheteux","year":"2021"},{"issue":"1","key":"2026091615504241800_bib11","doi-asserted-by":"publisher","first-page":"134","DOI":"10.1038\/s42003-022-03036-1","article-title":"Brains and algorithms partially converge in natural language processing","volume":"5","author":"Caucheteux","year":"2022","journal-title":"Communications Biology"},{"key":"2026091615504241800_bib12","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.2309.07311","article-title":"Sudden drops in the loss: Syntax acquisition, phase transitions, and simplicity bias in MLMs","author":"Chen","year":"2023","journal-title":"arXiv"},{"key":"2026091615504241800_bib13","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.1803.05457","article-title":"Think you have solved question answering? Try ARC, the AI2 Reasoning Challenge","author":"Clark","year":"2018","journal-title":"arXiv"},{"key":"2026091615504241800_bib14","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.2110.14168","article-title":"Training verifiers to solve math word problems","author":"Cobbe","year":"2021","journal-title":"arXiv"},{"issue":"17","key":"2026091615504241800_bib15","first-page":"259","article-title":"L\u00e9sions de la moiti\u00e9 gauche de l\u2019enc\u00e9phale co\u00efncidant avec l\u2019oubli des signes de la pens\u00e9e: Lu au Congr\u00e8s m\u00e9ridional tenu \u00e0 Montpellier en 1836, par le docteur Marc Dax","volume":"2","author":"Dax","year":"1865","journal-title":"Gazette Hebdomadaire de M\u00e9decine et de Chirurgie"},{"key":"2026091615504241800_bib16","doi-asserted-by":"publisher","first-page":"imag_a_00575","DOI":"10.1162\/imag_a_00575","article-title":"The Voxelwise Encoding Model framework: A tutorial introduction to fitting encoding models to fMRI data","volume":"3","author":"Dupr\u00e9 la Tour","year":"2025","journal-title":"Imaging Neuroscience"},{"key":"2026091615504241800_bib17","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.2402.00786","article-title":"CroissantLLM: A truly bilingual French-English language model","author":"Faysse","year":"2025","journal-title":"arXiv"},{"issue":"2","key":"2026091615504241800_bib18","doi-asserted-by":"publisher","first-page":"1177","DOI":"10.1152\/jn.00032.2010","article-title":"New method for fMRI investigations of language: Defining ROIs functionally in individual subjects","volume":"104","author":"Fedorenko","year":"2010","journal-title":"Journal of Neurophysiology"},{"issue":"3","key":"2026091615504241800_bib19","doi-asserted-by":"publisher","first-page":"628","DOI":"10.1162\/nol_e_00152","article-title":"Small but mighty: Ten myths and misunderstandings about the cerebellum","volume":"5","author":"Fiez","year":"2024","journal-title":"Neurobiology of Language"},{"key":"2026091615504241800_bib20","doi-asserted-by":"publisher","DOI":"10.5281\/zenodo.12608602","volume-title":"The language model evaluation harness","author":"Gao","year":"2024"},{"issue":"1","key":"2026091615504241800_bib21","doi-asserted-by":"publisher","first-page":"131","DOI":"10.1093\/brain\/90.1.131","article-title":"Language after section of the cerebral commissures","volume":"90","author":"Gazzaniga","year":"1967","journal-title":"Brain"},{"issue":"4","key":"2026091615504241800_bib22","doi-asserted-by":"publisher","first-page":"416","DOI":"10.1006\/nimg.1998.0419","article-title":"Deconvolution of impulse response in event-related BOLD fMRI","volume":"9","author":"Glover","year":"1999","journal-title":"NeuroImage"},{"issue":"3","key":"2026091615504241800_bib23","doi-asserted-by":"publisher","first-page":"369","DOI":"10.1038\/s41593-022-01026-4","article-title":"Shared computational principles for language processing in humans and deep language models","volume":"25","author":"Goldstein","year":"2022","journal-title":"Nature Neuroscience"},{"key":"2026091615504241800_bib24","doi-asserted-by":"publisher","first-page":"134","DOI":"10.1016\/j.cortex.2018.10.020","article-title":"Language lateralisation measured across linguistic and national boundaries","volume":"111","author":"Hausmann","year":"2019","journal-title":"Cortex"},{"key":"2026091615504241800_bib25","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.2111.09543","article-title":"DeBERTaV3: Improving DeBERTa using ELECTRA-style pre-training with gradient-disentangled embedding sharing","author":"He","year":"2023","journal-title":"arXiv"},{"issue":"5","key":"2026091615504241800_bib26","doi-asserted-by":"publisher","first-page":"393","DOI":"10.1038\/nrn2113","article-title":"The cortical organization of speech processing","volume":"8","author":"Hickok","year":"2007","journal-title":"Nature Reviews Neuroscience"},{"issue":"4","key":"2026091615504241800_bib27","doi-asserted-by":"publisher","first-page":"337","DOI":"10.1044\/1058-0360(2011\/10-0096)","article-title":"Language in the cerebellum","volume":"20","author":"Highnam","year":"2011","journal-title":"American Journal of Speech-Language Pathology"},{"issue":"1","key":"2026091615504241800_bib28","doi-asserted-by":"publisher","first-page":"43","DOI":"10.1162\/nol_a_00137","article-title":"Artificial neural network language models predict human brain responses to language even after a developmentally realistic amount of training","volume":"5","author":"Hosseini","year":"2024","journal-title":"Neurobiology of Language"},{"key":"2026091615504241800_bib29","doi-asserted-by":"publisher","first-page":"624","DOI":"10.18653\/v1\/2021.conll-1.49","article-title":"BabyBERTa: Learning more grammar with small-scale child-directed language","volume-title":"Proceedings of the 25th Conference on Computational Natural Language Learning","author":"Huebner","year":"2021"},{"issue":"3","key":"2026091615504241800_bib30","doi-asserted-by":"publisher","first-page":"90","DOI":"10.1109\/MCSE.2007.55","article-title":"Matplotlib: A 2D graphics environment","volume":"9","author":"Hunter","year":"2007","journal-title":"Computing in Science & Engineering"},{"issue":"7600","key":"2026091615504241800_bib31","doi-asserted-by":"publisher","first-page":"453","DOI":"10.1038\/nature17637","article-title":"Natural speech reveals the semantic maps that tile human cerebral cortex","volume":"532","author":"Huth","year":"2016","journal-title":"Nature"},{"key":"2026091615504241800_bib32","first-page":"6629","article-title":"Incorporating context into language encoding models for fMRI","volume-title":"Proceedings of the 32nd International Conference on Neural Information Processing Systems","author":"Jain","year":"2018"},{"issue":"5284","key":"2026091615504241800_bib33","doi-asserted-by":"publisher","first-page":"114","DOI":"10.1126\/science.274.5284.114","article-title":"Brain activation modulated by sentence comprehension","volume":"274","author":"Just","year":"1996","journal-title":"Science"},{"issue":"1","key":"2026091615504241800_bib34","doi-asserted-by":"publisher","first-page":"7","DOI":"10.1162\/nol_a_00116","article-title":"Lexical-semantic content, not syntactic structure, is the main contributor to ANN-brain similarity of fMRI responses in the language network","volume":"5","author":"Kauf","year":"2024","journal-title":"Neurobiology of Language"},{"key":"2026091615504241800_bib35","doi-asserted-by":"publisher","first-page":"101310","DOI":"10.1016\/j.cobeha.2023.101310","article-title":"A seat at the (language) table: Incorporating the cerebellum into frameworks for language processing","volume":"53","author":"LeBel","year":"2023","journal-title":"Current Opinion in Behavioral Sciences"},{"key":"2026091615504241800_bib36","doi-asserted-by":"publisher","first-page":"11260","DOI":"10.18653\/v1\/2024.findings-acl.671","article-title":"CMMLU: Measuring massive multitask language understanding in Chinese","volume-title":"Findings of the Association for Computational Linguistics: ACL 2024","author":"Li","year":"2024"},{"issue":"1","key":"2026091615504241800_bib37","doi-asserted-by":"publisher","first-page":"530","DOI":"10.1038\/s41597-022-01625-7","article-title":"Le Petit Prince multilingual naturalistic fMRI corpus","volume":"9","author":"Li","year":"2022","journal-title":"Scientific Data"},{"key":"2026091615504241800_bib38","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.2411.06096","article-title":"A systematic assessment of language models with linguistic minimal pairs in Chinese","author":"Liu","year":"2024","journal-title":"arXiv"},{"issue":"6","key":"2026091615504241800_bib39","doi-asserted-by":"publisher","first-page":"517","DOI":"10.1016\/j.tics.2024.01.011","article-title":"Dissociating language and thought in large language models","volume":"28","author":"Mahowald","year":"2024","journal-title":"Trends in Cognitive Sciences"},{"issue":"8","key":"2026091615504241800_bib40","doi-asserted-by":"publisher","first-page":"1014","DOI":"10.1038\/s41593-022-01114-5","article-title":"An investigation across 45 languages and 12 language families reveals a universal language network","volume":"25","author":"Malik-Moraleda","year":"2022","journal-title":"Nature Neuroscience"},{"key":"2026091615504241800_bib41","doi-asserted-by":"publisher","first-page":"56","DOI":"10.25080\/Majora-92bf1922-00a","article-title":"Data structures for statistical computing in Python","volume-title":"Proceedings of the 9th Python in Science Conference","author":"McKinney","year":"2010"},{"issue":"7","key":"2026091615504241800_bib42","doi-asserted-by":"publisher","first-page":"858","DOI":"10.1016\/j.cortex.2009.07.018","article-title":"The cerebellum and language: Historical perspective and review","volume":"46","author":"Murdoch","year":"2010","journal-title":"Cortex"},{"issue":"4","key":"2026091615504241800_bib43","doi-asserted-by":"publisher","first-page":"361","DOI":"10.1016\/0167-9473(88)90076-X","article-title":"Least orthogonal absolute deviations","volume":"6","author":"Nyquist","year":"1988","journal-title":"Computational Statistics & Data Analysis"},{"key":"2026091615504241800_bib44","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.2501.00656","article-title":"2 OLMo 2 Furious","author":"OLMo Team","year":"2024","journal-title":"arXiv"},{"key":"2026091615504241800_bib45","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.2209.11895","article-title":"In-context learning and induction heads","author":"Olsson","year":"2022","journal-title":"arXiv"},{"key":"2026091615504241800_bib46","doi-asserted-by":"publisher","first-page":"6505","DOI":"10.1038\/s41467-026-72916-5","article-title":"Precision fMRI reveals that the language network exhibits adult-like left-hemispheric lateralization by 4 years of age","volume":"17","author":"Ozernov-Palchik","year":"2026","journal-title":"Nature Communications"},{"issue":"4","key":"2026091615504241800_bib47","doi-asserted-by":"publisher","first-page":"611","DOI":"10.1162\/nol_a_00125","article-title":"Information-restricted neural language models reveal different brain regions\u2019 sensitivity to semantics, syntax, and context","volume":"4","author":"Pasquiou","year":"2023","journal-title":"Neurobiology of Language"},{"key":"2026091615504241800_bib48","first-page":"8026","article-title":"PyTorch: An imperative style, high-performance deep learning library","volume-title":"Proceedings of the 33rd International Conference on Neural Information Processing Systems","author":"Paszke","year":"2019"},{"key":"2026091615504241800_bib49","first-page":"2825","article-title":"Scikit-learn: Machine learning in Python","volume":"12","author":"Pedregosa","year":"2011","journal-title":"Journal of Machine Learning Research"},{"key":"2026091615504241800_bib50","volume-title":"Speech and brain mechanisms","author":"Penfield","year":"1959"},{"key":"2026091615504241800_bib51","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.2508.18226","article-title":"Disentangling the factors of convergence between brains and computer vision models","author":"Raugel","year":"2025","journal-title":"arXiv"},{"issue":"9","key":"2026091615504241800_bib52","doi-asserted-by":"publisher","first-page":"99","DOI":"10.1145\/3474381","article-title":"WinoGrande: An adversarial Winograd Schema Challenge at scale","volume":"64","author":"Sakaguchi","year":"2021","journal-title":"Communications of the ACM"},{"issue":"45","key":"2026091615504241800_bib53","doi-asserted-by":"publisher","first-page":"e2105646118","DOI":"10.1073\/pnas.2105646118","article-title":"The neural architecture of language: Integrative modeling converges on predictive processing","volume":"118","author":"Schrimpf","year":"2021","journal-title":"Proceedings of the National Academy of Sciences"},{"key":"2026091615504241800_bib54","first-page":"40699","article-title":"LLM circuit analyses are consistent across training and scale","volume-title":"Proceedings of the 38th International Conference on Neural Information Processing Systems","author":"Tigges","year":"2024"},{"key":"2026091615504241800_bib55","first-page":"14954","article-title":"Interpreting and improving natural-language processing (in machines) with natural language-processing (in the brain)","volume-title":"Proceedings of the 33rd International Conference on Neural Information Processing Systems","author":"Toneva","year":"2019"},{"key":"2026091615504241800_bib56","doi-asserted-by":"publisher","first-page":"314","DOI":"10.1016\/j.cortex.2016.05.013","article-title":"Multi-factorial modulation of hemispheric specialization and plasticity for language in healthy and pathological conditions: A review","volume":"86","author":"Tzourio-Mazoyer","year":"2017","journal-title":"Cortex"},{"issue":"2","key":"2026091615504241800_bib57","doi-asserted-by":"publisher","first-page":"22","DOI":"10.1109\/MCSE.2011.37","article-title":"The NumPy array: A structure for efficient numerical computation","volume":"13","author":"van der Walt","year":"2011","journal-title":"Computing in Science & Engineering"},{"issue":"3","key":"2026091615504241800_bib58","doi-asserted-by":"publisher","first-page":"261","DOI":"10.1038\/s41592-019-0686-2","article-title":"SciPy 1.0: Fundamental algorithms for scientific computing in Python","volume":"17","author":"Virtanen","year":"2020","journal-title":"Nature Methods"},{"issue":"2","key":"2026091615504241800_bib59","doi-asserted-by":"publisher","first-page":"266","DOI":"10.3171\/jns.1960.17.2.0266","article-title":"Intracarotid injection of sodium amytal for the lateralization of cerebral speech dominance: Experimental and clinical observations","volume":"17","author":"Wada","year":"1960","journal-title":"Journal of Neurosurgery"},{"key":"2026091615504241800_bib60","doi-asserted-by":"publisher","first-page":"377","DOI":"10.1162\/tacl_a_00321","article-title":"BLiMP: The benchmark of linguistic minimal pairs for English","volume":"8","author":"Warstadt","year":"2020","journal-title":"Transactions of the Association for Computational Linguistics"},{"key":"2026091615504241800_bib61","doi-asserted-by":"publisher","first-page":"625","DOI":"10.1162\/tacl_a_00290","article-title":"Neural network acceptability judgments","volume":"7","author":"Warstadt","year":"2019","journal-title":"Transactions of the Association for Computational Linguistics"},{"issue":"60","key":"2026091615504241800_bib62","doi-asserted-by":"publisher","first-page":"3021","DOI":"10.21105\/joss.03021","article-title":"seaborn: Statistical data visualization","volume":"6","author":"Waskom","year":"2021","journal-title":"Journal of Open Source Software"},{"issue":"3","key":"2026091615504241800_bib63","doi-asserted-by":"publisher","first-page":"641","DOI":"10.1093\/brain\/96.3.641","article-title":"Left hemisphere specialization for language in the newborn: Neuroanatomical evidence of asymmetry","volume":"96","author":"Witelson","year":"1973","journal-title":"Brain"},{"key":"2026091615504241800_bib64","doi-asserted-by":"publisher","first-page":"38","DOI":"10.18653\/v1\/2020.emnlp-demos.6","article-title":"Transformers: State-of-the-art natural language processing","volume-title":"Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing: System Demonstrations","author":"Wolf","year":"2020"},{"key":"2026091615504241800_bib65","doi-asserted-by":"publisher","first-page":"4791","DOI":"10.18653\/v1\/P19-1472","article-title":"HellaSwag: Can a machine really finish your sentence?","volume-title":"Proceedings of the 57th Annual Meeting of the Association for Computational Linguistics","author":"Zellers","year":"2019"}],"container-title":["Neurobiology of Language"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/direct.mit.edu\/nol\/article-pdf\/doi\/10.1162\/NOL.a.284\/2614204\/nol.a.284.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/direct.mit.edu\/nol\/article-pdf\/doi\/10.1162\/NOL.a.284\/2614204\/nol.a.284.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T19:50:54Z","timestamp":1789588254000},"score":1,"resource":{"primary":{"URL":"https:\/\/direct.mit.edu\/nol\/article\/doi\/10.1162\/NOL.a.284\/137653\/Left-Right-Asymmetry-in-Predicting-Brain-Activity"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026]]},"references-count":65,"URL":"https:\/\/doi.org\/10.1162\/nol.a.284","relation":{},"ISSN":["2641-4368"],"issn-type":[{"value":"2641-4368","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2026]]},"published":{"date-parts":[[2026]]},"article-number":"NOL.a.284"}}