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Description
Magnetophosphenes are visual sensations perceived as flashes of light when exposed to a time varying magnetic field. Their perception threshold serves as a key parameter in defining human exposure limits. While previous studies have primarily relied on subjective button-press reporting, electroencephalography (EEG) offers an objective approach to investigating neural correlates of magnetophosphene perception. However, traditional spectral analysis methods often fail to detect subtle dynamic changes in EEG signals. In this study, we applied Recurrence Quantification Analysis (RQA) to assess nonlinear dynamics in EEG signals recorded from 20 healthy participants exposed to 50 Hz sinusoidal magnetic fields (50 mT). Participants were equipped with a 64-channel MRI-compatible EEG cap, and magnetophosphene perception was recorded via button-press responses. Spectral analysis (Welch’s method) was conducted to examine power variations in alpha and beta bands, while RQA extracted nonlinear features such as Recurrence Rate (RR) and Determinism (DET). The results are still being analyzed, but we expect no significant differences in spectral power between perception (50 mT) and no perception (0 mT) conditions. However, we anticipate that RQA will reveal increased signal regularity during magnetic field exposure, evidenced by a rise in DET. These findings would suggest that RQA is more sensitive than frequency-based methods for detecting subtle EEG structural changes associated with magnetophosphene perception. This study underscores the relevance of nonlinear EEG analysis techniques in bioelectromagnetics research and the potential of RQA in studying neural responses to electromagnetic fields.
