title: A time-variant processing approach for the analysis of alpha and gamma MEG oscillations during flicker stimulus generated entrainment.
abstract: Repetitive flicker stimulation (photic driving) offers the possibility to study the properties and coupling characteristics of stimulation-sensitive neuronal oscillators by means of the MEG/EEG analysis. With flicker frequencies in the region of the individual alpha band frequency, the dynamics of the entrainment process of the alpha oscillation, as well as the dynamics of the accompanying gamma oscillations and the coupling between the oscillations, are investigated by means of an appropriate combination of time-variant analysis methods. The Hilbert and the Gabor transformation reveal time-variant properties (frequency entrainment, phase locking, and n:m synchronization) of the entrainment process in the whole frequency range. Additionally, time-variant partial directed coherence is applied to identify ocular saccadic interferences and to study the directed information transfer between the recording sites of the simultaneously derived MEG/EEG data during the entrainment. The MEG data is the focus of this methodological study as the entrainment effects of the alpha oscillation are stronger in MEG than in the EEG. The occipital brain region (visual cortex) was mainly investigated and the dynamics of the alpha entrainment quantified. It can be shown that at the beginning of this entrainment, a transient, strongly phase-locked "40-Hz" gamma oscillation occurs.
authors.affiliation: Institute of Medical Statistics, Computer Sciences and Documentation, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany. matthias.wacker@mti.uni-jena.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Wacker
authors.forename: Miroslav
authors.initials: M
authors.lastname: Galicki
authors.forename: Peter
authors.initials: P
authors.lastname: Putsche
authors.forename: Thomas
authors.initials: T
authors.lastname: Milde
authors.forename: Karin
authors.initials: K
authors.lastname: Schwab
authors.forename: Jens
authors.initials: J
authors.lastname: Haueisen
authors.forename: Carolin
authors.initials: C
authors.lastname: Ligges
authors.forename: Herbert
authors.initials: H
authors.lastname: Witte
mesh_terms: D000328:Adult; D000465:Algorithms; D058407:Electroencephalography Phase Synchronization / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D015999:Multivariate Analysis; D010775:Photic Stimulation; D012815:Signal Processing, Computer-Assisted; D014793:Visual Cortex / Q000502:physiology*