University of Washington

Department of Rehabilitation Medicine

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Comparison of subdural and subgaleal recordings of cortical high-gamma oscillations in humans


Olson JD, Wander JD, Johnson LA, Sarma D, Weaver KE, Novotny EJ, Ojemann JG, Darvas F



Publication Info:

Clinical Neurophysiology, 2015 Apr 9:pii: S1388-2457(15)00230-8


OBJECTIVE: The purpose of this study is to determine the relationship between cortical electrophysiological (CE) signals recorded from the surface of the brain (subdural electrocorticography, or ECoG) and signals recorded extracranially from the subgaleal (SG) space.
METHODS: We simultaneously recorded several hours of continuous ECoG and SG signals from 3 human pediatric subjects, and compared power spectra of signals between a differential SG montage and several differential ECoG montages to determine the nature of the transfer function between them.
RESULTS: We demonstrate the presence of CE signals in the SG montage in the high-gamma range (HG, 70-110Hz), and the transfer function between 70 and 110Hz is best characterized as a linear function of frequency. We also test an alternative transfer function, i.e. a single pole filter, to test the hypothesis of frequency dependent attenuation in that range, but find this model to be inferior to the linear model.
CONCLUSIONS: Our findings indicate that SG electrodes are capable of recording HG signals without frequency distortion compared with ECoG electrodes. SIGNIFICANCE: HG signals could be recorded minimally invasively from outside the skull, which could be important for clinical care or brain-computer interface applications.

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