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

Abstract

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, 70–110 Hz), and the transfer function between 70 and 110 Hz 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.

Increased Gamma Brainwave Amplitude Compared to Control in Three Different Meditation Traditions

“…Physiological studies support the hypothesis of a role of 30 to 100 Hz gamma synchronization in facilitating the neuronal communication underlying conscious awareness in a meaningful way [22, 24]. Although frequently thought to be filtered out by skull and scalp tissues [55], high frequency gamma activity recorded on the scalp has been related to enhanced top-down control in vision [56], with strongest gamma power preceding fastest reaction time, and audition [57]. In addition, a magneto-encephalographic study reports a role of gamma >55 Hz in visual object coding (binding process) [58] and intracranial recording of EEG from the ventral occipito-temporal cortex also reported increased high frequency broadband gamma power related to selective attention [59].…”

Cortical Topography of Error-Related High-Frequency Potentials During Erroneous Control in a Continuous Control Brain–Computer Interface

“…The typical coverage and high temporal resolution of EEG, relative to fMRI, allow for the identification of wide-spread voltage changes in response to error. However, because EEG is non-invasive, electrical signals from the cortex attenuate and diffuse as they travel up through the skull, leading to lower signal-to-noise ratio (SNR) and challenges in source localization (Jatoi et al, 2014; Olson et al, 2016). To circumvent some of these limitations, we investigate error-related potentials in a one-dimensional brain–computer interface (BCI) task using subdural electrocorticography (ECoG) in human subjects.…”

Continuous decoding of human grasp kinematics using epidural and subdural signals

“…Previous studies that examined the effect of the dura and CSF on neural signals concentrated primarily on the relative power spectra or amplitude of the signals (Slutzky et al 2010, Bundy et al 2014, Olson et al 2015). Here, we evaluated how useful these signals would be for BMIs by using them to decode hand movements.…”