Talking to the brain: Using Large Language Models as Proxies to Model Brain Semantic Representation

Traditional psychological experiments utilizing naturalistic stimuli face challenges in manual annotation and ecological validity. To address this, we introduce a novel paradigm leveraging multimodal large language models (LLMs) as proxies to extract rich semantic information from naturalistic images through a Visual Question Answering (VQA) strategy for analyzing human visual semantic representation. LLM-derived repres entations successfully predict esta blished neural activity patterns measured by fMRI (e.g., faces, buildings), validatin g its feasibility and revealing hierarchical semantic organization across cortical regions. A brain semantic network constructed from LLM-derived representations identifies meaningful clusters refl ecting functional and contextual associations. This innovative methodology offers a powerful solution fo r investigating brain semantic organization with naturalistic stimuli, overcoming limitations of traditional annotation methods and paving the way for more ecologically valid explorations of human cognition.