{'fraction_non_alphanumeric': 0.038461538461538464, 'fraction_numerical': 0.008097165991902834, 'mean_word_length': 5.337606837606837, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
MEG-recording of DC fields using a 151-channel whole-head device

Several physiological and pathophysiological phenomena are known to cause slow shifts of the electrical brain potential. Previous studies could also demonstrate slowly time-varying neuromagnetic fields (DC fields, f < 0:1 Hz) in several conditions (e.g., hyperventilation [1, 2], anoxic depolarization [3], focal ischemia [4]). The non-invasive magnetoencephalography (MEG) measures electrophysiological parameters remotely. Therefore, it is not prone to impedance changes at the electrodetissue interface like the electroencephalography, which hinder long-term recordings of DC shifts. The increase of magnetic noise in the low frequency domain (1=f noise) interferes with the measurement of the neuronal DC fields. Nevertheless, recent studies have shown the feasibility of DC recordings based on the periodic movement of the source even in a noisy clinical environment [2, 5]. By modulating the source position, i.e., the head, with respect to the detector, the DC magnetic field is shifted to a higher frequency where less environmental noise is present. Based on this concept, a new technique to measure DC fields using whole-head magnetoencephalography (MEG) was developed. A device for moving the head and a continuous head localization were implemented and validated. In order to explore the capabilities of the method, artificial fields of a magnetic dipole phantom and biomagnetic fields were investigated.