Multitaper Spectral Estimation HDP-HMMs for EEG Sleep Inference
This work addresses the need for automated and personalized sleep state analysis in EEG monitoring for sleep disorder diagnostics and research, though it is incremental as it builds on existing HDP-HMM and spectral estimation techniques.
The paper tackled the problem of subjective and time-consuming manual classification of EEG sleep stages by proposing a data-driven method using a Hierarchical Dirichlet Process Hidden Markov Model with multitaper spectral estimation, resulting in an automated algorithm that recovers sleep dynamics, identifies subject-specific microstates, and discovers shared spectral signatures across subjects.
Electroencephalographic (EEG) monitoring of neural activity is widely used for sleep disorder diagnostics and research. The standard of care is to manually classify 30-second epochs of EEG time-domain traces into 5 discrete sleep stages. Unfortunately, this scoring process is subjective and time-consuming, and the defined stages do not capture the heterogeneous landscape of healthy and clinical neural dynamics. This motivates the search for a data-driven and principled way to identify the number and composition of salient, reoccurring brain states present during sleep. To this end, we propose a Hierarchical Dirichlet Process Hidden Markov Model (HDP-HMM), combined with wide-sense stationary (WSS) time series spectral estimation to construct a generative model for personalized subject sleep states. In addition, we employ multitaper spectral estimation to further reduce the large variance of the spectral estimates inherent to finite-length EEG measurements. By applying our method to both simulated and human sleep data, we arrive at three main results: 1) a Bayesian nonparametric automated algorithm that recovers general temporal dynamics of sleep, 2) identification of subject-specific "microstates" within canonical sleep stages, and 3) discovery of stage-dependent sub-oscillations with shared spectral signatures across subjects.