Juggler’s ASR: Unpacking the principles of artifact subspace reconstruction for revision toward extreme MoBI
Hyeonseok Kim, Chi-Yuan Chang, Christian Kothe, John R. Iversen, Makoto Miyakoshi
Abstract
To improve the Artifact Subspace Reconstruction (ASR) algorithm's performance for real-world EEG data by addressing the problem of low-quality or no calibration data identification in the original ASR (ASR original ) algorithm. We proposed a new method for defining high-quality calibration data using point-by-point amplitude evaluation to eliminate collateral rejection of clean data, which is identified as the major cause of the problem with ASR original . We compared non-parametric and parametric approaches, namely Density-Based Spatial Clustering of Applications with Noise (DBSCAN) and the Generalized Extreme Value (GEV) distribution (ASR DBSCAN and ASR GEV , respectively). We demonstrated the effectiveness of these approaches on simulated and real EEG data. Simulation results showed that ASR DBSCAN and ASR GEV removed simulated artifacts completely where ASR original failed, both in time- and frequency-domain evaluations. In empirical data from 205-channel EEG recordings during a three-ball juggling task (n=13), ASR DBSCAN found 42% and ASR GEV found 24% of data usable for calibration on average, compared to only 9% by ASR original . Subsequent Independent Component Analysis (ICA) showed that data preprocessed with ASR DBSCAN and ASR GEV produced brain ICs that accounted for more variance of the original data (30% and 29%) compared to ASR original (26%). The proposed ASR DBSCAN and ASR GEV methods handle motion-related artifacts better than the original ASR algorithm, enabling researchers to better extract brain activity during real-world motor tasks. These methods provide a practical advantage in processing EEG data from experiments involving high-intensity motor activities, advancing biomedical research capabilities. • We developed new algorithms that can handle high-frequency motion artifacts when using artifact subspace reconstruction (ASR). • The proposed methods better handle EEG data with highly non-stationary noise typically due to high-intensity motor execution under the real-world conditions. • We clarified the reason, at least in part, why a counterintuitively large number of standard deviations has been recommended as a cutoff threshold in the literature on ASR applications.