title: Comparison of subdural and subgaleal recordings of cortical high-gamma activity in humans.
abstract: OBJECTIVE
  The purpose of this study is to determine the relationship between cortical electrophysiological (CE) signals recorded from the surface of the brain (subdural electrocorticography, or ECoG) and signals recorded extracranially from the subgaleal (SG) space.
  
  
  METHODS
  We simultaneously recorded several hours of continuous ECoG and SG signals from 3 human pediatric subjects, and compared power spectra of signals between a differential SG montage and several differential ECoG montages to determine the nature of the transfer function between them.
  
  
  RESULTS
  We demonstrate the presence of CE signals in the SG montage in the high-gamma range (HG, 70-110 Hz), and the transfer function between 70 and 110 Hz is best characterized as a linear function of frequency. We also test an alternative transfer function, i.e. a single pole filter, to test the hypothesis of frequency dependent attenuation in that range, but find this model to be inferior to the linear model.
  
  
  CONCLUSIONS
  Our findings indicate that SG electrodes are capable of recording HG signals without frequency distortion compared with ECoG electrodes.
  
  
  CONCLUSIONS
  HG signals could be recorded minimally invasively from outside the skull, which could be important for clinical care or brain-computer interface applications.
authors.affiliation: University of Washington, Department of Rehabilitation Medicine, USA; University of Washington, Center for Sensorimotor Neural Engineering, USA. Electronic address: jaredol@uw.edu.
authors.forename: Jared D
authors.initials: JD
authors.lastname: Olson
authors.affiliation: University of Washington, Center for Sensorimotor Neural Engineering, USA; University of Washington, Department of Bioengineering, USA. Electronic address: jdwander@uw.edu.
authors.forename: Jeremiah D
authors.initials: JD
authors.lastname: Wander
authors.affiliation: University of Washington, Center for Sensorimotor Neural Engineering, USA; University of Washington, Department of Neurological Surgery, USA. Electronic address: liseaj@uw.edu.
authors.forename: Lise
authors.initials: L
authors.lastname: Johnson
authors.affiliation: University of Washington, Center for Sensorimotor Neural Engineering, USA; University of Washington, Department of Bioengineering, USA. Electronic address: dsarma@uw.edu.
authors.forename: Devapratim
authors.initials: D
authors.lastname: Sarma
authors.affiliation: University of Washington, Center for Sensorimotor Neural Engineering, USA; University of Washington, Department of Radiology, USA. Electronic address: weaverk@uw.edu.
authors.forename: Kurt
authors.initials: K
authors.lastname: Weaver
authors.affiliation: University of Washington, Center for Sensorimotor Neural Engineering, USA; University of Washington, Department of Neurology, USA; University of Washington, Department of Pediatrics, USA. Electronic address: ejn4@uw.edu.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Novotny
authors.affiliation: University of Washington, Center for Sensorimotor Neural Engineering, USA; University of Washington, Department of Neurological Surgery, USA; University of Washington, Department of Radiology, USA; University of Washington, Seattle Children's Hospital Division of Neurosurgery, USA. Electronic address: jojemann@u.washington.edu.
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Ojemann
authors.affiliation: University of Washington, Center for Sensorimotor Neural Engineering, USA; University of Washington, Department of Neurological Surgery, USA. Electronic address: fdarvas@uw.edu.
authors.forename: Felix
authors.initials: F
authors.lastname: Darvas
mesh_terms: D002540:Cerebral Cortex / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D000069280:Electrocorticography / Q000295:instrumentation / Q000379:methods*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D013355:Subdural Space / Q000502:physiology*
keywords: Brain computer interface; Electrocorticography; Electroencephalography; High-gamma brain machine interface; Subgaleal