title: Targeting the parahippocampal area by auditory cortex stimulation in tinnitus.
abstract: BACKGROUND
  The final common pathway in tinnitus generation is considered to be synchronized auditory oscillatory hyperactivity. Intracranial auditory cortex stimulation (iACS) via implanted electrodes has been developed to treat severe cases of intractable tinnitus targeting this final common pathway, in the hope of being a panacea for tinnitus. However, not everybody responds to this treatment.
  
  
  OBJECTIVE
  The electrical brain activity and functional connectivity at rest might determine who is going to respond or not to iACS and might shed light on the pathophysiology of auditory phantom sound generation.
  
  
  METHODS
  The resting state electrical brain activity of 5 patients who responded and 5 patients who did not respond to auditory cortex implantation are compared using source localized spectral activity (Z-score of log transformed current density) and lagged phase synchronization.
  
  
  RESULTS
  sLORETA source localization reveals significant differences between responders vs non-responders for beta3 in left posterior parahippocampal, hippocampal and amygdala area extending into left insula. Gamma band differences exist in the posterior parahippocampal areas and BA10. Functional connectivity between the auditory cortex and the hippocampal area is increased for beta2, delta and theta2 in responders, as well as between the parahippocampal area and auditory cortex for beta3.
  
  
  CONCLUSIONS
  The resting state functional connectivity and activity between the auditory cortex and parahippocampus might determine whether a tinnitus patient will respond to a cortical implant. The auditory cortex may only be a functional entrance into a larger parahippocampal based tinnitus network.
authors.affiliation: Brai²n, Sint Augustinus Hospital, Antwerp, Belgium; Department of Surgical Sciences, Section of Neurosurgery, Dunedin School of Medicine, University of Otago, New Zealand. Electronic address: dirk.deridder@otagao.ac.nz.
authors.forename: Dirk
authors.initials: D
authors.lastname: De Ridder
authors.affiliation: School for Behavioral & Brain Sciences, University of Texas at Dallas, Dallas, USA; Department of Translational Neuroscience, Faculty of Medicine, University of Antwerp, Belgium.
authors.forename: Sven
authors.initials: S
authors.lastname: Vanneste
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D001303:Auditory Cortex / Q000503:physiopathology*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006624:Hippocampus / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D020534:Parahippocampal Gyrus / Q000503:physiopathology*; D014012:Tinnitus / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy*
keywords: Auditory cortex; EEG; Electrodes; Functional connectivity; Gamma; Phase synchronization; Tinnitus; sLORETA