title: A novel technique for quantitative bedside monitoring of neurovascular coupling.
abstract: BACKGROUND
  There is no current method for continuous quantification of neurovascular coupling (NVC) in spontaneous brain activity. To fill this void, we propose a novel method to quantify NVC using electroencephalogram (EEG) and near-infrared spectroscopy (NIRS) data.
  
  
  METHODS
  Since EEG and NIRS measure physiologic changes occurring at different time scales, we bring them into a common dynamical time frame (DTF). To achieve this, we partition both signals into one-second epochs and calculate the standard deviation of the EEG and the average value of the NIRS for each epoch. We then quantify the NVC by calculating spectral coherence between the two signals in the DTF. The resulting NVC will have a low resolution with all of its content localized below 1Hz.
  
  
  RESULTS
  After validating this framework on simulated data, we applied this approach to EEG and NIRS signals collected from four term infants undergoing therapeutic hypothermia for neonatal encephalopathy. Two of these infants showed no evidence of structural brain injury, and the other two died during the course of the therapy. The intact survivors showed emergence of NVC during hypothermia and/or after rewarming. In contrast, the two critically ill infants, who subsequently died, lacked this feature.
  
  
  METHODS
  Existing methods quantify NVC by averaging neurovascular signals based on certain events (for example seizure) in the EEG activity, whereas our approach quantifies coupling between spontaneous background EEG and NIRS.
  
  
  CONCLUSIONS
  Real-time continuous monitoring of NVC may be a promising physiologic signal for cerebral monitoring in future.
authors.affiliation: Division of Fetal and Transitional Medicine, Fetal Medicine Institute, Children's National Health System, 111 Michigan Ave NW, Washington, DC 20010, USA. Electronic address: rgovinda@childrensnational.org.
authors.forename: R B
authors.initials: RB
authors.lastname: Govindan
authors.affiliation: Division of Neonatology, Children's National, 111 Michigan Ave NW, Washington, DC 20010, USA.
authors.forename: An
authors.initials: A
authors.lastname: Massaro
authors.affiliation: Division of Neurology, Children's National, 111 Michigan Ave NW, Washington, DC 20010, USA.
authors.forename: Taeun
authors.initials: T
authors.lastname: Chang
authors.affiliation: Division of Diagnostic Imaging and Radiology, Children's National, 111 Michigan Ave NW, Washington, DC 20010, USA.
authors.forename: Gilbert
authors.initials: G
authors.lastname: Vezina
authors.affiliation: Division of Fetal and Transitional Medicine, Fetal Medicine Institute, Children's National Health System, 111 Michigan Ave NW, Washington, DC 20010, USA.
authors.forename: Adré
authors.initials: A
authors.lastname: du Plessis
mesh_terms: D003198:Computer Simulation; D004569:Electroencephalography / Q000379:methods* / Q000592:standards; D006801:Humans; D007036:Hypothermia, Induced; D020925:Hypoxia-Ischemia, Brain / Q000175:diagnosis* / Q000503:physiopathology; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases; D008959:Models, Neurological; D064926:Neurophysiological Monitoring / Q000379:methods* / Q000592:standards; D000069336:Neurovascular Coupling / Q000502:physiology*; D015203:Reproducibility of Results; D019265:Spectroscopy, Near-Infrared / Q000379:methods* / Q000592:standards; D013997:Time Factors
keywords: Electroencephalogram; Hypoxic ischemic encephalopathy; Near-infrared spectroscopy; Neurovascular coupling; Spectral coherence