title: Correlation networks for identifying changes in brain connectivity during epileptiform discharges and transcranial magnetic stimulation.
abstract: The occurrence of epileptiform discharges (ED) in electroencephalographic (EEG) recordings of patients with epilepsy signifies a change in brain dynamics and particularly brain connectivity. Transcranial magnetic stimulation (TMS) has been recently acknowledged as a non-invasive brain stimulation technique that can be used in focal epilepsy for therapeutic purposes. In this case study, it is investigated whether simple time-domain connectivity measures, namely cross-correlation and partial cross-correlation, can detect alterations in the connectivity structure estimated from selected EEG channels before and during ED, as well as how this changes with the application of TMS. The correlation for each channel pair is computed on non-overlapping windows of 1 s duration forming weighted networks. Further, binary networks are derived by thresholding or statistical significance tests (parametric and randomization tests). The information for the binary networks is summarized by statistical network measures, such as the average degree and the average path length. Alterations of brain connectivity before, during and after ED with or without TMS are identified by statistical analysis of the network measures at each state.
authors.affiliation: Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece. esingiri@auth.gr.
authors.forename: Elsa
authors.initials: E
authors.lastname: Siggiridou
authors.affiliation: Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece. dkugiu@auth.gr.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kugiumtzis
authors.affiliation: Laboratory of Clinical Neurophysiology, AHEPA Hospital, Medical School, Thessaloniki 54124, Greece. kimiskid@med.auth.gr.
authors.forename: Vasilios K
authors.initials: VK
authors.lastname: Kimiskidis
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D063132:Connectome / Q000379:methods*; D003627:Data Interpretation, Statistical; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000503:physiopathology*; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D009415:Nerve Net / Q000503:physiopathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D050781:Transcranial Magnetic Stimulation / Q000379:methods*