Multimodal EEG-IMU Fusion for Motor Assessment: Leveraging Task-Dependent Complementarity for Robustness

Abstract

Movement disorders such as Parkinson&#39;s disease require comprehensive motor assessment, but reliable digital assessment pipelines integrating multiple sensing modalities across diverse motor tasks remain insufficiently characterized. We present a proof-of-concept study evaluating task-specific modality performance and multimodal fusion across ten motor activities. Synchronized EEG-IMU data were recorded from six participants (52 recording pairs). We evaluated an EEGNet + Transformer model for 16-channel EEG (125 Hz) and XGBoost on hand-crafted accelerometer and gyroscope features (25 Hz). Under 5-fold cross-validation in a subject-dependent setting, IMU achieved 94.41+/-0.58% accuracy and outperformed EEG on 7 of 10 activities, while EEG achieved 92.82+/-1.45% and showed lower error for rhythmic cycling (4.03% vs. 12.10%). Late fusion via logistic regression reached 98.68+/-0.32%, giving an 81.5% error reduction versus EEG alone and improving worst-task accuracy from approximately 87% for a single modality to 96.76%. Fusion also reduced cross-task performance variance from approximately 3% to 1.06% (paired t-test, p < 0.001, df = 4; p-values approximate given fold dependence), showing more uniform reliability across the assessment battery. Although the small sample limits generalizability, these results suggest that EEG and IMU provide asymmetric, task-dependent strengths and that late fusion can leverage this complementarity to improve assessment reliability. This study provides methodological and empirical motivation for larger-scale clinical validation in movement disorder populations.