title: Analysis of infant cortical synchrony is constrained by the number of recording electrodes and the recording montage.
abstract: OBJECTIVE
  To assess how the recording montage in the neonatal EEG influences the detection of cortical source signals and their phase interactions.
  
  
  METHODS
  Scalp EEG was simulated by forward modeling 20-200 simultaneously active sources covering the cortical surface of a realistic neonatal head model. We assessed systematically how the number of scalp electrodes (11-85), analysis montage, or the size of cortical sources affect the detection of cortical phase synchrony. Statistical metrics were developed for quantifying the resolution and reliability of the montages.
  
  
  RESULTS
  The findings converge to show that an increase in the number of recording electrodes leads to a systematic improvement in the detection of true cortical phase synchrony. While there is always a ceiling effect with respect to discernible cortical details, we show that the average and Laplacian montages exhibit superior specificity and sensitivity as compared to other conventional montages.
  
  
  CONCLUSIONS
  Reliability in assessing true neonatal cortical synchrony is directly related to the choice of EEG recording and analysis configurations. Because of the high conductivity of the neonatal skull, the conventional neonatal EEG recordings are spatially far too sparse for pertinent studies, and this loss of information cannot be recovered by re-montaging during analysis.
  
  
  CONCLUSIONS
  Future neonatal EEG studies will need prospective planning of recording configuration to allow analysis of spatial details required by each study question. Our findings also advice about the level of details in brain synchrony that can be studied with existing datasets or by using conventional EEG recordings.
authors.affiliation: Neuroscience Center, University of Helsinki, Helsinki, Finland; Department of Children's Clinical Neurophysiology, HUS Medical Imaging Center and Children's Hospital, Helsinki University Central Hospital and University of Helsinki, Helsinki, Finland. Electronic address: anton.tokariev@helsinki.fi.
authors.forename: Anton
authors.initials: A
authors.lastname: Tokariev
authors.affiliation: Department of Children's Clinical Neurophysiology, HUS Medical Imaging Center and Children's Hospital, Helsinki University Central Hospital and University of Helsinki, Helsinki, Finland.
authors.forename: Sampsa
authors.initials: S
authors.lastname: Vanhatalo
authors.affiliation: Neuroscience Center, University of Helsinki, Helsinki, Finland.
authors.forename: J Matias
authors.initials: JM
authors.lastname: Palva
mesh_terms: D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D003344:Cortical Synchronization / Q000502:physiology*; D004566:Electrodes; D004569:Electroencephalography / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011446:Prospective Studies
keywords: Brain development; Connectivity; Dense array EEG; Forward model; Neonatal EEG; Simulation