title: Visually evoked phase synchronization changes of alpha rhythm in migraine: correlations with clinical features.
abstract: OBJECTIVE
  This study aimed to compute phase synchronization of the alpha band from a multichannel electroencephalogram (EEG) recorded under repetitive flash stimulation from migraine patients without aura. This allowed examination of ongoing EEG activity during visual stimulation in the pain-free phase of migraine.
  
  
  METHODS
  Flash stimuli at frequencies of 3, 6, 9, 12, 15, 18, 21, 24, and 27 Hz were delivered to 15 migraine patients without aura and 15 controls, with the EEG recorded from 18 scalp electrodes, referred to the linked earlobes. The EEG signals were filtered in the alpha (7.5-13 Hz) band. For all stimulus frequencies that we evaluated, the phase synchronization index was based on the Hilbert transformation.
  
  
  RESULTS
  Phase synchronization separated the patients and controls for the 9, 24 and 27 Hz stimulus frequencies; hyper phase synchronization was observed in patients, whereas healthy subjects were characterized by a reduced phase synchronization. These differences were found in all regions of the scalp.
  
  
  CONCLUSIONS
  During migraine, the brain synchronizes to the idling rhythm of the visual areas under certain photic stimulations; in normal subjects however, brain regions involved in the processing of sensory information demonstrate desynchronized activity. Hypersynchronization of the alpha rhythm may suggest a state of cortical hypoexcitability during the interictal phase of migraine.
  
  
  CONCLUSIONS
  The employment of non-linear EEG analysis may identify subtle functional changes in the migraine brain.
authors.affiliation: TIRES: Center of Innovative Technologies for Signal Detection and Processing, Bari, Italy. m.detommaso@neurol.uniba.it
authors.forename: Marina
authors.initials: M
authors.lastname: de Tommaso
authors.forename: Daniele
authors.initials: D
authors.lastname: Marinazzo
authors.forename: Marco
authors.initials: M
authors.lastname: Guido
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Libro
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Stramaglia
authors.forename: Luigi
authors.initials: L
authors.lastname: Nitti
authors.forename: Gianluca
authors.initials: G
authors.lastname: Lattanzi
authors.forename: Leonardo
authors.initials: L
authors.lastname: Angelini
authors.forename: Mario
authors.initials: M
authors.lastname: Pellicoro
mesh_terms: D000328:Adult; D000513:Alpha Rhythm; D001931:Brain Mapping; D003344:Cortical Synchronization; D004307:Dose-Response Relationship, Radiation; D004569:Electroencephalography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008881:Migraine Disorders / Q000503:physiopathology*; D010775:Photic Stimulation / Q000379:methods; D011336:Probability