Computational protocol: Functional connectivity changes detected with magnetoencephalography after mild traumatic brain injury

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Protocol publication

[…] The MEG multichannel recordings were preprocessed using Matlab (The MathWorks, Inc., Natick, MA, USA) and Fieldtrip (). Axial gradiometer data were originally collected at a sampling rate of 1017.25 Hz and bandpassed between 0.1–200 Hz using hardware filters, whereas the planar gradiometer data were collected at 1000 Hz and bandpass filtered via software between 0.1–200 Hz. Artifact reduction was performed based on independent component analysis (ICA) as implemented in the EEGLAB toolbox (). The extended Informax algorithm (; ; ) was used to remove components associated with eye, muscle, and cardiac artifactual activity (, ). In addition to visually inspecting the time course and topographical layout of all ICs, we estimated their kurtosis and skewness values. Components reflecting cardiac activity were recognized from their typical rhythmic pattern in the time domain and their widespread topography. ICs related to muscle activity were identified based on statistical measures (kurtosis higher than a predefined threshold, kurtthr = 12, determined empirically), spectral characteristics (increased energy in the frequency range between 20–60 Hz), and topographies encompassing temporal brain areas (; , ). Artifactual ICs were zeroed, whereas the remaining ICs were used to generate artifact-free signals that were back-projected to the original MEG sensor space via the inverse ICA transformation.Occasionally, activity from a bad sensor was replaced with the interpolated activity of its immediate neighbors after applying ICA to avoid introducing dependencies in the recordings. Line noise was removed using a notch filter at 60 Hz. This interpolation procedure was necessary for five control and two mTBI subjects for at most four MEG sensors. […]

Pipeline specifications

Software tools FieldTrip, EEGLAB
Application Clinical electrophysiology
Organisms Homo sapiens
Diseases Brain Injuries