Systematic Comparison of Signal Quality in Portable and Wearable Wireless EEG Devices: Methods and Standards

Electroencephalography (EEG) is a technique that captures the electrical activity of the cerebral cortex, effectively reflecting various rapid cognitive processes. Traditional EEG devices, often large and bulky, are impractical for real-world applications. To address this, wearable and wireless EEG systems have been developed as cutting-edge technology. However, there remains uncertainty about their signal quality .In this study, we introduce a systematic comparison method customized for portable wireless EEG devices. This experiment includes three tasks: α-suppression, Biofeedback, and the Stroop Colour and Word Test, evaluating signal quality in both time and frequency domains. In the α-suppression task, we analyzed spectral power in the α band, Signal-to-Noise Ratio (SNR), Root Mean Square(RMS),and artifact rejection. For the biofeedback task, we evaluated Engagement (β/(α+θ)) and Relaxation (α/β) indices. We also measured the N400 amplitude during the Stroop Colour and Word Test. These indicators represent varying levels of signal quality requirements, from low to high. Additionally, to assess whether semi-dry EEG devices can match the performance of medical-grade gel electrodes, further significant difference and correlation analysis between the two types of devices were conducted. The frequency domain analysis revealed alpha suppression during eyes-open states and increased relaxation and engagement states during the biofeedback task compared to resting state. In the time domain analysis, although no statistical significance was observed in the N400 component, a clear trend of a larger N400 under inconsistent conditions was evident in waveform and topographic maps. Furthermore, difference tests and correlation analysis between the two devices demonstrated a strong positive correlation in signals and consistent performance across all tasks. These findings suggest that portable EEG devices provide reliable signal accuracy in real-world settings, the signal quality of the semi-dry electrodes used in this study is comparable to that of medical-grade gel electrodes.