Optimal Time Window and Frequency Bandwidth Parameter Combination for Subject-Specific Motor Imagery EEG Classification

TL;DR

This study systematically evaluates how optimizing time windows and frequency bands improves subject-specific motor imagery EEG classification accuracy, revealing significant differences and optimal parameter combinations.

Contribution

It introduces a comprehensive method for optimizing both temporal and spectral parameters simultaneously, demonstrating improved classification performance in MI EEG analysis.

Findings

Significant differences in accuracy across different time windows and frequency bands.

Optimal combination identified as 0-4 seconds at 4-12 Hz for all subjects.

Personalized parameter optimization enhances MI EEG classification.

Abstract

Motor-imagery (MI) EEG can be classified using supervised machine learning techniques such as Linear Discriminant Analysis applied to features extracted by Common Spatial Patterns. Performance of these models varies widely, possibly due to MI studies commonly utilising differing post-cue time windows and frequency bands to one another. This study aims to assess how the simultaneous optimisation of both these parameters impact MI classification performance. This is done by iteratively training and testing a series of subject-specific models on different combinations of frequency bandwidth and time window options across 109 subjects. This is followed by a statistical analysis using repeated measures ANOVA to uncover significant differences between different bandwidths and time windows in terms of accuracy across the patient cohort. The resulting visualisations and statistical tests show that there are, indeed, significant differences between both specific time windows and specific bandwidths in terms of accuracy. While the comparison of classification accuracies across 23 frequency bandwidths during five different time windows demonstrates an optimal temporal and spectral scale combination of (0, 4) s at the range of (4, 12) Hz across all subjects, the subjects demonstrate similar accuracies for other parameter combinations. These findings highlight the efficacy of personalised models to detect optimal temporal and spectral parameter combinations to best classify MI EEG signals that inherently vary across subjects.