title: Direct Causal Networks for the Study of Transcranial Magnetic Stimulation Effects on Focal Epileptiform Discharges.
abstract: BACKGROUND
  Transcranial magnetic stimulation (TMS) can have inhibitory effects on epileptiform discharges (EDs) of patients with focal seizures. However, the brain connectivity before, during and after EDs, with or without the administration of TMS, has not been extensively explored.
  
  
  OBJECTIVE
  To investigate the brain network of effective connectivity during ED with and without TMS in patients with focal seizures.
  
  
  METHODS
  For the effective connectivity a direct causality measure is applied termed partial mutual information from mixed embedding (PMIME). TMS-EEG data from two patients with focal seizures were analyzed. Each EEG record contained a number of EDs in the majority of which TMS was administered over the epileptic focus. As a control condition, sham stimulation over the epileptogenic zone or real TMS at a distance from the epileptic focus was also performed. The change in brain connectivity structure was investigated from the causal networks formed at each sliding window.
  
  
  CONCLUSIONS
  The PMIME could detect distinct changes in the network structure before, within, and after ED. The administration of real TMS over the epileptic focus, in contrast to sham stimulation, terminated the ED prematurely in a node-specific manner and regained the network structure as if it would have terminated spontaneously.
authors.affiliation: Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kugiumtzis
authors.affiliation: Laboratory of Clinical Neurophysiology, Medical School, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
authors.forename: Vasilios K
authors.initials: VK
authors.lastname: Kimiskidis
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods*; D004828:Epilepsies, Partial / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007257:Information Theory; D009434:Neural Pathways / Q000503:physiopathology; D012640:Seizures / Q000503:physiopathology; D012815:Signal Processing, Computer-Assisted; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
keywords: Transcranial magnetic stimulation; brain connectivity; direct causality; electroencephalogram; epileptiform discharges; information measures