Abstract
The discrete sampling of the brain’s electrical field at the scalp surface with individual recording sensors is subject to the same sampling error as the discrete sampling of the time series at any one sensor with analog-to-digital conversion. Unlike temporal sampling, spatial sampling is intrinsically discrete, so that the post hoc application of analog anti-aliasing filters is not possible. However, the skull acts as a low-pass spatial filter of the brain’s electrical field, attenuating the high spatial frequency information. Because of the skull’s spatial filtering, a discrete sampling of the spatial field with a reasonable number of scalp electrodes is possible. In this paper, we provide theoretical and experimental evidence that adequately sampling the human electroencephalograph (EEG) across the full surface of the head requires a minimum of 128 sensors. Further studies with each of the major EEG and event-related potential phenomena are required in order to determine the spatial frequency of these phenomena and in order to determine whether additional increases in sensor density beyond 128 channels will improve the spatial resolution of the scalp EEG.
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Note: Electrical Geodesics, Inc. sells 64-, 128-, and 256-channel EEG systems and thus has a commercial interest in promoting dense sensor array technology.—Editor
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Srinivasan, R., Tucker, D.M. & Murias, M. Estimating the spatial Nyquist of the human EEG. Behavior Research Methods, Instruments, & Computers 30, 8–19 (1998). https://doi.org/10.3758/BF03209412
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DOI: https://doi.org/10.3758/BF03209412