NeuralFieldManifold: Reconstruction of LFP manifold with Lag Embedding

Local field potentials (LFPs) are population-level neural signals central to brain-computer interfaces and systems neuroscience, yet unlike spike-based population codes, their dynamics lack a principled geometric description that connects spectral structure to latent state-space geometry. Here we establish, analytically and empirically, that the lag-embedded dynamics of LFP signals lie on a low-dimensional K-torus, where K equals the number of sustained oscillatory modes present in the signal. Modeling LFPs as bounded autoregressive processes, we show that each oscillatory component contributes an independent circular degree of freedom, while aperiodic 1/f structure and noise contribute only geometric thickness around the manifold without altering its topology. To apply this theory to real nonstationary recordings, we introduce DeepLagField, a physics-informed network that jointly estimates time-varying AR structure and effective model order, with formal guarantees that local toroidal geometry is preserved despite drifting oscillatory dynamics.We validate the predicted toroidal geometry using persistent homology across primate visual cortex LFP, rodent hippocampal LFP, and mouse cortical EEG recordings, confirming the expected Betti number signatures across species and recording modalities. Critically, we demonstrate that this geometric structure is not merely descriptive but carries behaviorally relevant information inaccessible to standard spectral summaries — as evidenced by torus parameters derived purely from manifold geometry outperforming multi-band spectral features for sleep-state decoding without any hand-crafted frequency design. This proof of concept points toward broad downstream utility wherever oscillatory field signals are recorded, from neural decoding and brain-state monitoring to clinical biomarker development. These results reframe neural oscillations not as isolated spectral features but as coordinate directions of a low-dimensional delay manifold, opening a geometry-first approach to neural signal analysis that is simultaneously theoretically grounded, empirically validated across species, and predictive of behaviorally relevant brain states.