Biology subjects

Kubo, R.

Publications and source records attributed to Kubo, R..

5 recordsLinked to original sources

bioRxiv2025

Second Language Proficiency Modulates Hierarchical Alignment between Brain Activity and Large Language Models

Second language (L2) comprehension is thought to proceed hierarchically, from basic word recognition to complex discourse-level understanding. However, the neural mechanisms underpinning this hierarchical progression remain poorly understood. Leveraging the hierarchical nature of linguistic representations in large language models (LLMs), we investigated how L2 proficiency modulates layer-wise brain-LLM alignment. Using functional magnetic resonance imaging (fMRI) data collected during discourse listening from 54 participants with varying levels of L2 proficiency, we constructed individualized encoding models to quantify how proficiency shapes the brain-LLM representational correspondence. In high-proficiency individuals, LLM-based models reliably predicted neural responses in a distributed network comprising temporal, frontal, and medial-parietal cortices, while for low-proficiency participants, prediction performance decreased. Notably, alignment in the superior temporal sulcus (STS) showed a robust correlation with L2 proficiency at mid-to-deep LLM layers, suggesting that the STS encodes higher-level linguistic abstractions essential for advanced language comprehension. These findings indicate that L2 proficiency modulates the alignment between LLMs and the brain in a graded, layer-dependent manner, providing insights into hierarchical neural language representations.

neuroscience↗

bioRxiv2024

The Brain Tells a Story: Unveiling Distinct Representations of Semantic Content in Speech, Objects, and Stories in the Human Brain with Large Language Models

In recent studies, researchers have used large language models (LLMs) to explore semantic representations in the brain; however, they have typically assessed different levels of semantic content, such as speech, objects, and stories, separately. In this study, we recorded brain activity using functional magnetic resonance imaging (fMRI) while participants viewed 8.3 hours of dramas and movies. We annotated these stimuli at multiple semantic levels, which enabled us to extract latent representations of LLMs for this content. Our findings demonstrate that LLMs predict human brain activity more accurately than traditional language models, particularly for complex background stories. Furthermore, we identify distinct brain regions associated with different semantic representations, including multi-modal vision-semantic representations, which highlights the importance of modeling multi-level and multi-modal semantic representations simultaneously. We will make our fMRI dataset publicly available to facilitate further research on aligning LLMs with human brain function. Please check out our webpage at https://sites.google.com/view/llm-and-brain/.

neuroscience↗

bioRxiv2024

Cortical representational geometry of diverse tasks reveals subject-specific and subject-invariant cognitive structures

The variability in brain function forms the basis for our uniqueness. Prior studies indicate smaller individual differences and larger inter-subject correlation (ISC) in sensorimotor areas than in the association cortex. These studies, deriving information from brain activity, leave individual differences in cognitive structures based on task similarity relations unexplored. This study quantitatively evaluates these differences by integrating ISC, representational similarity analysis, and vertex-wise encoding models using functional magnetic resonance imaging across 25 cognitive tasks. ISC based on cognitive structures enables subject identification with 100% accuracy using at least 14 tasks. ISC is larger in the fronto-parietal association and higher-order visual cortices, suggesting subject-invariant cognitive structures in these regions. Principal component analysis reveals different cognitive structure configurations within these regions. This study provides new evidence of individual variability and similarity in abstract cognitive structures.

neuroscience↗

bioRxiv2023

Cortical representations of languages during natural dialogue

Individuals integrate their own words, their partners words, and the context of dialogue into coherent meanings. Research suggests that mutual understanding between speakers and listeners is supported by a shared representation between language production and comprehension1,2. However, it remains unknown how languages are represented in the brain during dialogue, which is characterized by dynamic, adaptive behaviours such as turn-taking3,4. Here, we used functional magnetic resonance imaging (fMRI) to compare language production and comprehension maps obtained from natural dialogue in the same participants to show that separate representations exist for language production and comprehension. While production showed selectivity towards the motor system and comprehension towards the auditory system, both production and comprehension were represented in broadly distributed regions. These separate representations were similar in amodal brain regions that integrate semantic5,6 and pragmatic information7,8, and provide a common ground for mutual understanding1,2, reflecting dynamic, complementary roles in interactive language use, including turn-taking3,4,9, backchannels10, and fillers11. Our findings suggest that separate and analogous linguistic representations for production and comprehension are interwoven in the same networks that underlie complementary interactions and making sense in dialogue.

neuroscience↗

bioRxiv2020

Analysis of healthy reference ranges for clinically relevant gut microbial indicators: A large web-based cohort study in Japan

BackgroundAlthough several large cohort studies have focused on the human gut microbiome, large cohort study of the Japanese gut microbiome is scarce, especially that of healthy or non-diseased individuals. The purpose of this study was to establish a reference range for gut microbial indices by collecting Japanese real-world microbiome data from a Mykinso cohort. MethodsWe collected stool samples and original survey on lifestyle from 5,843 Japanese people through Mykinso gut microbiome testing service. From the obtained 16S rRNA sequence data derived from the stool sample, the ratio and distribution of each taxon were analyzed. The relationship between different epidemiological attributes and gut microbial indicators were statistically tested. ResultsThe qualitative and quantitative indicators of these common gut microbiota were confirmed to be strongly correlated with age, sex, constipation/diarrhea, and history of lifestyle-related diseases. Therefore, we set up the healthy sub-cohort that controlled for these attribute factors, and defined a reference range from the distribution of gut microbial index in that population. ConclusionsThe gut microbiota of Japanese people had high beta diversity, and there was no single "typical" gut microbiota type. We believe that the reference range of the gut microbial index obtained in this study can be a new reference value for determining the balance and health of the gut microbiota of an individual. In the future, it is necessary to clarify the clinical validity of this reference value by comparing with the clinical disease cohort.

microbiology↗