{'fraction_non_alphanumeric': 0.025835866261398176, 'fraction_numerical': 0.004559270516717325, 'mean_word_length': 5.230283911671925, 'pattern_counts': {'":': 0, '<': 0, '<?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}}
A Practical Non-Cephalic Reference Electrode: The Stephenson-Gibbs Non-Cephalic System

Introduction The usefulness of a non-cephalic reference electrode has always been recognized in electroencephalography. Various reference sites such as the ear lobe, mastoid, nose, chin, mandible, midline and common average reference all introduce artifact into the record or themselves pick up varying amounts of EEG activity. The major problem with a non-cephalic reference is that the EKG R-wave amplitude is approximately one millivolt when recorded between cephalic and non-cephalic electrodes. Therefore, the extent to which the EKG can be rendered equipotential, thus reducing the R wave artifact, determines the utility of a non-cephalic reference in routine EEG recordings. Stephenson and Gibbs (1), described a noncephalic reference system which utilizes a potentiometer between electrodes on the cervical spine (C7), and the suprasternal notch. In the average adult the EKG's recorded between the scalp and either the suprasternal notch or C7 are of opposite polarity and approximately equipotential. MacGillivray et al. (2), note that it is difficult to balance out all of the EKG when many electrodes are widely spaced over the scalp. They attribute this to changes in the cardiac axis with respiration. For this reason they conclude that EKG artifact precludes routine use of this reference. This non-cephalic neck and chest (N&C) reference of Stephenson-Gibbs (1) has been used routinely since 1950 in adult EEG's performed at the Clinical Neurophysiology Laboratory of the Massachusetts General Hospital. In those patients in whom the EKG artifact could not be adequately removed using this technique, other references such as ears or common average were chosen. We present below the results of using the N&C reference technique in a large group of consecutive unselected patient recordings, with respect to the interference of EKG artifact on EEG interpretation. Method