title: Wavelet entropy analysis of event-related potentials indicates modality-independent theta dominance.
abstract: Sensory/cognitive stimulation elicits multiple electroencephalogram (EEG)-oscillations that may be partly or fully overlapping over the time axis. To evaluate co-existent multi-frequency oscillations, EEG responses to unimodal (auditory or visual) and bimodal (combined auditory and visual) stimuli were analyzed by applying a new method called wavelet entropy (WE). The method is based on the wavelet transform (WT) and quantifies entropy of short segments of the event-related brain potentials (ERPs). For each modality, a significant transient decrease of WE emerged in the post-stimulus EEG epoch indicating a highly-ordered state in the ERP. WE minimum was always determined by a prominent dominance of theta (4-8 Hz) ERP components over other frequency bands. Event-related 'transition to order' was most pronounced and stable at anterior electrodes, and after bimodal stimulation. Being consistently observed across different modalities, a transient theta-dominated state may reflect a processing stage that is obligatory for stimulus evaluation, during which interfering activations from other frequency networks are minimized.
authors.affiliation: Institute of Physiology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 23, 1113 Sofia, Bulgaria. jyord@iph.bio.bas.bg
authors.forename: Juliana
authors.initials: J
authors.lastname: Yordanova
authors.forename: Vasil
authors.initials: V
authors.lastname: Kolev
authors.forename: Osvaldo A
authors.initials: OA
authors.lastname: Rosso
authors.forename: Martin
authors.initials: M
authors.lastname: Schürmann
authors.forename: Oliver W
authors.initials: OW
authors.lastname: Sakowitz
authors.forename: Murat
authors.initials: M
authors.lastname: Ozgören
authors.forename: Erol
authors.initials: E
authors.lastname: Basar
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000513:Alpha Rhythm; D001307:Auditory Perception / Q000502:physiology*; D001611:Beta Rhythm; D001683:Biological Clocks / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D003700:Delta Rhythm; D019277:Entropy; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000502:physiology; D009474:Neurons / Q000502:physiology; D010775:Photic Stimulation; D012044:Regression Analysis; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013826:Theta Rhythm / Q000295:instrumentation / Q000379:methods*; D013997:Time Factors; D014796:Visual Perception / Q000502:physiology*