BrainSymphony: A parameter-efficient multimodal foundation model for brain dynamics with limited data

A lightweight foundation model called BrainSymphony integrates fMRI time series and diffusion-derived structural connectivity, enabling unimodal or multimodal training without architectural changes and requiring less data than larger models. It processes fMRI data through parallel spatial and temporal transformer streams, distills embeddings via a Perceiver module, and encodes anatomical connectivity with a signed graph transformer. The model outperforms larger counterparts on benchmarks for prediction, classification, and network discovery. Attention maps from an independent psilocybin dataset reveal drug-induced reorganization of cortical hierarchies, demonstrating interpretability and generalizability. The work shows that architecturally informed multimodal models can surpass much larger models, advancing AI applications in neuroscience.

Study at a glance

Abstract

Foundation models are transforming neuroscience but are often prohibitively large, data-hungry, and difficult to deploy. Here, we introduce BrainSymphony, a lightweight and parameter-efficient foundation model with plug-and-play integration of fMRI time series and diffusion-derived structural connectivity, allowing unimodal or multimodal training and deployment without architectural changes while requiring substantially less data compared to the state-of-the-art. The model processes fMRI time series through parallel spatial and temporal transformer streams, distilled into compact embeddings by a Perceiver module, while a novel signed graph transformer encodes anatomical connectivity from diffusion MRI. These complementary representations are then combined through an adaptive fusion mechanism. Despite its compact design, BrainSymphony consistently outperforms larger models on benchmarks spanning prediction, classification, and unsupervised network discovery. Highlighting the model's generalizability and interpretability, attention maps reveal drug-induced context-dependent reorganization of cortical hierarchies in an independent psilocybin neuroimaging dataset. BrainSymphony delivers accessible, interpretable, and clinically meaningful results and demonstrates that architecturally informed, multimodal models can surpass much larger counterparts and advance applications of AI in neuroscience.