title: Transcranial focused ultrasound modulates intrinsic and evoked EEG dynamics.
abstract: BACKGROUND
  The integration of EEG recordings and transcranial neuromodulation has provided a useful construct for noninvasively investigating the modification of human brain circuit activity. Recent evidence has demonstrated that focused ultrasound can be targeted through the human skull to affect the amplitude of somatosensory evoked potentials and its associated spectral content.
  
  
  OBJECTIVE
  The present study tests whether focused ultrasound transmitted through the human skull and targeted to somatosensory cortex can affect the phase and phase rate of cortical oscillatory dynamics.
  
  
  METHODS
  A computational model was developed to gain insight regarding the insertion behavior of ultrasound induced pressure waves in the human head. The instantaneous phase and phase rate of EEG recordings before, during, and after transmission of transcranial focused ultrasound (tFUS) to human somatosensory cortex were examined to explore its effects on phase dynamics.
  
  
  RESULTS
  Computational modeling results show the skull effectively reinforces the focusing of tFUS due to curvature of material interfaces. Neurophysiological recordings show that tFUS alters the phase distribution of intrinsic brain activity for beta frequencies, but not gamma. This modulation was accompanied by a change in phase rate of both beta and gamma frequencies. Additionally, tFUS modulated phase distributions in the beta band of early sensory-evoked activity but did not affect late sensory-evoked activity, lending support to the spatial specificity of tFUS for neuromodulation. This spatial specificity was confirmed through an additional experiment where the ultrasound transducer was moved 1 cm laterally from the original cortical target.
  
  
  CONCLUSIONS
  Focused ultrasonic energy can alter EEG oscillatory dynamics through local mechanical perturbation of discrete cortical circuits.
authors.affiliation: School of Biomedical Engineering and Sciences, Virginia Tech, Blacksburg, VA 24061, USA; Virginia Tech Carilion Research Institute, Roanoke, VA 24015, USA.
authors.forename: Jerel
authors.initials: J
authors.lastname: Mueller
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Minnesota, MN 55455, USA.
authors.forename: Wynn
authors.initials: W
authors.lastname: Legon
authors.affiliation: Virginia Tech Carilion Research Institute, Roanoke, VA 24015, USA; Department of Clinical Neurophysiology, Georg-August-University, Göttingen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Opitz
authors.affiliation: Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Tomokazu F
authors.initials: TF
authors.lastname: Sato
authors.affiliation: School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85287, USA. Electronic address: wtyler@asu.edu.
authors.forename: William J
authors.initials: WJ
authors.lastname: Tyler
mesh_terms: D000293:Adolescent; D000328:Adult; D058256:Brain Waves / Q000502:physiology*; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D013003:Somatosensory Cortex / Q000502:physiology*; D013016:Sound; D055815:Young Adult
keywords: Electroencephalography (EEG); Neuromodulation; Oscillations; Phase; Ultrasound