2010/03/29 by Nima Dehghani, Claude Bédard, Dehghani, Nima +7
Neuroscience · #EEG and Brain-Computer Interfaces #FOS: Biological sciences #Functional Brain Connectivity Studies #Neural dynamics and brain function #Neurons and Cognition (q-bio.NC)
paper · pdf · doi:10.48550/arxiv.1003.5538
openalex publication_date 2010/03/29 · openalex created_date 2025/10/24 · openalex updated_date 2026/07/28
The resistive or non-resistive nature of the extracellular space in the brain\nis still debated, and is an important issue for correctly modeling\nextracellular potentials. Here, we first show theoretically that if the medium\nis resistive, the frequency scaling should be the same for electroencephalogram\n(EEG) and magnetoencephalogram (MEG) signals at low frequencies (<10 Hz). To\ntest this prediction, we analyzed the spectrum of simultaneous EEG and MEG\nmeasurements in four human subjects. The frequency scaling of EEG displays\ncoherent variations across the brain, in general between 1/f and 1/f2, and\ntends to be smaller in parietal/temporal regions. In a given region, although\nthe variability of the frequency scaling exponent was higher for MEG compared\nto EEG, both signals consistently scale with a different exponent. In some\ncases, the scaling was similar, but only when the signal-to-noise ratio of the\nMEG was low. Several methods of noise correction for environmental and\ninstrumental noise were tested, and they all increased the difference between\nEEG and MEG scaling. In conclusion, there is a significant difference in\nfrequency scaling between EEG and MEG, which can be explained if the\nextracellular medium (including other layers such as dura matter and skull) is\nglobally non-resistive.\n