Title: Uni-NTFM: A Unified Foundation Model for EEG Signal Representation Learning
Primary area: applications to neuroscience & cognitive science
Keywords: Brain Computer interface, Foundation Model, Electroencephalography

Abstract: Foundation models pretrained on various and unlabeled data have demonstrated significant success in natural language and vision, but their application to electroencephalography (EEG) remains challenged due to the signal's unique properties. Existing brain foundation models that inherit architectures designed for text or images lead to three limitations in pre-training: 1) conflating time-domain waveform patterns with frequency-domain rhythmic features in a single processing stream, 2) ignoring the critical spatial topology of  electrodes with different standards, and 3) reliance on the inflexible, dense network to process functionally distinct EEG patterns. To address these challenges, we introduce the \textbf{Unified Neural Topological Foundation Model (Uni-NTFM)}, which is designed based on neuroscience principles to produce universal and interpretable representations. Uni-NTFM integrates three core innovations: 1) A decoupled architecture parallelly encodes time, frequency, and raw signal representations before performing cross-domain feature integration; 2) A topological embedding mechanism to unify electrodes from different international standards and generate structured input sequences for brain regions; and 3) a  Mixture-of-Experts neural Transformer that efficiently scales model capacity by routing signal patterns to specialized subnetworks. The largest model, Uni-NTFM$_{large}$, has a record-breaking 1.9B parameters and was pretrained on over 28,000 hours of diverse EEG data via a dual-domain masked reconstruction objective. Uni-NTFM significantly outperforms existing task-specific methods and foundation models across nine distinct downstream tasks under both linear probing and fine-tuning settings, demonstrating a superior ability to learn universal representations of brain activity. Our code is available at \url{https://anonymous.4open.science/r/Uni-NTFM-0924}.