Resting-State EEG Biomarkers of Tinnitus Robust to Cross-Subject and Cross-Platform Variation

TL;DR

This study identifies EEG-derived features, especially Koopman eigenvalue magnitude, as robust biomarkers for tinnitus that generalize across different datasets and platforms.

Contribution

It demonstrates that PCA-based Koopman features outperform microstate features in cross-dataset tinnitus classification, highlighting oscillation stability as a key biomarker.

Findings

Koopman eigenvalue magnitude correlates with tinnitus across datasets.

Microstate transition features are less robust than Koopman features.

Oscillation decay rates, not frequency shifts, serve as reliable tinnitus biomarkers.

Abstract

Tinnitus is a prevalent auditory condition lacking objective biomarkers, motivating the search for reliable neural signatures. EEG, being a noninvasive method of brain imaging with a high temporal resolution provides a way to investigate the neural dynamics that may be associated with tinnitus. The generalizability of EEG-based tinnitus biomarkers across different datasets remains a critical challenge. Microstate theory has allowed for the characterization of quasi-stable topographic configurations in EEG, with some studies reporting altered microstate dynamics in tinnitus patients. This work seeks to improve upon existing dynamical systems analysis and their viability in identifying a robust biomarker. Dynamical features were extracted from two resting-state EEG datasets for the binary classification of tinnitus. Here, robustness is quantified as cross-dataset generalization, which is critical for clinical translation. We employ microstate analysis by identifying topographic states, from which transition probability and state duration features are derived. We also apply Koopman operator analysis through Dynamic Mode Decomposition (DMD) to dimensionality-reduced EEG to extract features in single-window. A linear SVM is trained on each feature set and evaluated in a cross-dataset generalization paradigm. PCA-based Koopman features yield the strongest discrimination metrics across both transfer directions, outperforming microstate-derived features. A Wasserstein-distance consistency analysis further reveals that Koopman eigenvalue \emph{magnitude}, encoding oscillation stability, generalizes across datasets ($\bar{\rho} = 0.685$), whereas eigenvalue \emph{phase}, encoding oscillation frequency, does not ($\bar{\rho} = 1.583$), providing interpretable evidence that altered oscillatory decay rates, rather than frequency shifts, constitute the more robust tinnitus biomarker.