title: Electrical probing of cortical excitability in patients with epilepsy.
abstract: Standard methods for seizure prediction involve passive monitoring of intracranial electroencephalography (iEEG) in order to track the 'state' of the brain. This paper introduces a new method for measuring cortical excitability using an electrical probing stimulus. Electrical probing enables feature extraction in a more robust and controlled manner compared to passively tracking features of iEEG signals. The probing stimuli consist of 100 bi-phasic pulses, delivered every 10 min. Features representing neural excitability are estimated from the iEEG responses to the stimuli. These features include the amplitude of the electrically evoked potential, the mean phase variance (univariate), and the phase-locking value (bivariate). In one patient, it is shown how the features vary over time in relation to the sleep-wake cycle and an epileptic seizure. For a second patient, it is demonstrated how the features vary with the rate of interictal discharges. In addition, the spatial pattern of increases and decreases in phase synchrony is explored when comparing periods of low and high interictal discharge rates, or sleep and awake states. The results demonstrate a proof-of-principle for the method to be applied in a seizure anticipation framework. This article is part of a Supplemental Special Issue entitled The Future of Automated Seizure Detection and Prediction.
authors.affiliation: Department of Electrical and Electronic Engineering, University of Melbourne, Parkville, VIC, 3010, Australia. deanrf@unimelb.edu.au
authors.forename: Dean R
authors.initials: DR
authors.lastname: Freestone
authors.forename: Levin
authors.initials: L
authors.lastname: Kuhlmann
authors.forename: David B
authors.initials: DB
authors.lastname: Grayden
authors.forename: Anthony N
authors.initials: AN
authors.lastname: Burkitt
authors.forename: Alan
authors.initials: A
authors.lastname: Lai
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Nelson
authors.forename: Simon
authors.initials: S
authors.lastname: Vogrin
authors.forename: Michael
authors.initials: M
authors.lastname: Murphy
authors.forename: Wendyl
authors.initials: W
authors.lastname: D'Souza
authors.forename: Radwa
authors.initials: R
authors.lastname: Badawy
authors.forename: Dragan
authors.initials: D
authors.lastname: Nesic
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Cook
mesh_terms: D000465:Algorithms; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000473:pathology* / Q000503:physiopathology; D005071:Evoked Potentials / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors