title: Problem of signal contamination in interhemispheric dual-sided subdural electrodes.
abstract: Dual-sided subdural electrodes are used in the localization and lateralization of seizure-onset zones when the area of interest is within the interhemispheric fissure. We designed the current study to test the validity of the assumption that each side of the dual-sided electrodes records from the hemisphere it faces. We recorded with dual-sided strip and grid electrodes implanted in the occipital interhemispheric space in two patients with nonoccipital epilepsy during two visual stimulation tasks in which subjects were presented with visual stimuli in the ipsilateral or contralateral visual hemifields. Our findings show substantial contamination of recordings from the opposite hemisphere. Although, as expected, electrodes recording through the falx record faintly from the contralateral cortical surface, they unexpectedly pick up strong signals from the cortex behind them. Therefore, we conclude that these electrodes should not be used for lateralization of the origin of epileptic activity or evoked responses.
authors.affiliation: Laboratory of Behavioral & Cognitive Neurology, Department of Neurology & Neurological Sciences, Stanford University, Stanford, California 94305, USA.
authors.forename: George
authors.initials: G
authors.lastname: Nune
authors.forename: Jonathan
authors.initials: J
authors.lastname: Winawer
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Rauschecker
authors.forename: Mohammad
authors.initials: M
authors.lastname: Dastjerdi
authors.forename: Brett L
authors.initials: BL
authors.lastname: Foster
authors.forename: Brian
authors.initials: B
authors.lastname: Wandell
authors.forename: Josef
authors.initials: J
authors.lastname: Parvizi
mesh_terms: D000328:Adult; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D010775:Photic Stimulation; D013355:Subdural Space; D014793:Visual Cortex / Q000503:physiopathology