Attribution and Application of Multiple Neurons in Multimodal Large Language Models

Feiyu Wang, Ziran Zhao, Dong Yu, Pengyuan Liu


Abstract
Multimodal Large Language Models (MLLMs) have demonstrated exceptional performance across various tasks. However, the internal mechanisms by which they interpret and integrate cross-modal information remain insufficiently understood. In this paper, to address the limitations of prior studies that could only identify neurons corresponding to single-token and rely on the vocabulary of LLMs, we propose a novel method to identify multimodal neurons in Transformer-based MLLMs. Then we introduce fuzzy set theory to model the complex relationship between neurons and semantic concepts and to characterize how multiple neurons collaboratively contribute to semantic concepts. Through both theoretical analysis and empirical validation, we demonstrate the effectiveness of our method and present some meaningful findings. Furthermore, by modulating neuron activation values based on the constructed fuzzy sets, we enhance performance on the Visual Question Answering (VQA) task, showing the practical value of our approach in downstream applications in MLLMs.
Anthology ID:
2025.findings-emnlp.625
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2025
Month:
November
Year:
2025
Address:
Suzhou, China
Editors:
Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
11649–11662
Language:
URL:
https://aclanthology.org/2025.findings-emnlp.625/
DOI:
Bibkey:
Cite (ACL):
Feiyu Wang, Ziran Zhao, Dong Yu, and Pengyuan Liu. 2025. Attribution and Application of Multiple Neurons in Multimodal Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2025, pages 11649–11662, Suzhou, China. Association for Computational Linguistics.
Cite (Informal):
Attribution and Application of Multiple Neurons in Multimodal Large Language Models (Wang et al., Findings 2025)
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https://aclanthology.org/2025.findings-emnlp.625.pdf
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