title: Evoked phase synchronization between adjacent high-density electrodes in human scalp EEG: duration and time course related to behavior.
abstract: OBJECTIVE
  Data from a previous event-related potential (ERP) study in visual-perceptual grouping [Nikolaev AR, van Leeuwen C. Flexibility in spatial and non-spatial feature grouping: an event-related potentials study. Brain Res Cogn Brain Res 2004;22:13-25] were re-analyzed to identify event-related dynamics of phase-synchronization.
  
  
  METHODS
  In 20 Hz activity, uniform spreading of phase synchronization in closely spaced (approximately 2 cm) scalp electrodes appears and disappears spontaneously. The lengths of synchronized activity intervals and how they vary as a function of stimulus presentation were compared between task and control conditions.
  
  
  RESULTS
  Synchronization reached a maximum in the task condition about 180 ms post-stimulus onset, coinciding with the peak N180 ERP marking the deployment of task-specific attention. Synchronized intervals were longer in the task than in the control condition. Long (above 80 ms) intervals occurred at a stable rate before and just after stimulus onset, but steeply decreased 200-400 ms afterwards.
  
  
  CONCLUSIONS
  Perceptual tasks lead to longer synchronized intervals in early visual areas. Attention deployment resets the ongoing synchronization. Event-related activity, besides low-frequency ERP, consists of high-frequency short and long synchronized intervals corresponding to evoked bursts and ongoing oscillations, respectively.
  
  
  CONCLUSIONS
  High-density scalp recorded EEG revealed synchronization dynamics in a local, early visual area of cortex that can be interpreted as modulation of spontaneous ongoing task-related processes by attention.
authors.affiliation: RIKEN Brain Science Institute, Wako-shi, Japan. nikolaev@brain.riken.jp
authors.forename: Andrey R
authors.initials: AR
authors.lastname: Nikolaev
authors.forename: Pulin
authors.initials: P
authors.lastname: Gong
authors.forename: Cees
authors.initials: C
authors.lastname: van Leeuwen
mesh_terms: D000328:Adult; D000465:Algorithms; D001519:Behavior / Q000502:physiology*; D003344:Cortical Synchronization; D003627:Data Interpretation, Statistical; D004566:Electrodes; D004569:Electroencephalography; D004585:Electrooculography; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D014796:Visual Perception / Q000502:physiology