title: In-vivo measurements of human brain tissue conductivity using focal electrical current injection through intracerebral multicontact electrodes.
abstract: In-vivo measurements of human brain tissue conductivity at body temperature were conducted using focal electrical currents injected through intracerebral multicontact electrodes. A total of 1,421 measurements in 15 epileptic patients (age: 28 ± 10) using a radiofrequency generator (50 kHz current injection) were analyzed. Each contact pair was classified as being from healthy (gray matter, n = 696; white matter, n = 530) or pathological (epileptogenic zone, n = 195) tissue using neuroimaging analysis of the local tissue environment and intracerebral EEG recordings. Brain tissue conductivities were obtained using numerical simulations based on conductivity estimates that accounted for the current flow in the local brain volume around the contact pairs (a cube with a side length of 13 mm). Conductivity values were 0.26 S/m for gray matter and 0.17 S/m for white matter. Healthy gray and white matter had statistically different median impedances (P < 0.0001). White matter conductivity was found to be homogeneous as normality tests did not find evidence of multiple subgroups. Gray matter had lower conductivity in healthy tissue than in the epileptogenic zone (0.26 vs. 0.29 S/m; P = 0.012), even when the epileptogenic zone was not visible in the magnetic resonance image (MRI) (P = 0.005). The present in-vivo conductivity values could serve to create more accurate volume conduction models and could help to refine the identification of relevant intracerebral contacts, especially when located within the epileptogenic zone of an MRI-invisible lesion. Hum Brain Mapp 38:974-986, 2017. © 2016 Wiley Periodicals, Inc.
authors.affiliation: CNRS, CRAN, UMR 7039, Vandœuvre-lès-Nancy, France.|Université de Lorraine, CRAN, UMR 7039, Vandœuvre-lès-Nancy, 54516, France.|Service de Neurologie, Centre Hospitalier Universitaire de Nancy, Nancy, 54000, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Koessler
authors.affiliation: Service de Neurochirurgie, Centre Hospitalier Universitaire de Nancy, Nancy, 54000, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Colnat-Coulbois
authors.affiliation: CNRS, CRAN, UMR 7039, Vandœuvre-lès-Nancy, France.|Université de Lorraine, CRAN, UMR 7039, Vandœuvre-lès-Nancy, 54516, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Cecchin
authors.affiliation: Ventspils Engineering Research Institute, Ventspils University, Ventspils, LV3601, Latvia.
authors.forename: Janis
authors.initials: J
authors.lastname: Hofmanis
authors.affiliation: Department of Biomedical Engineering, City College of New York, New York, New York.
authors.forename: Jacek P
authors.initials: JP
authors.lastname: Dmochowski
authors.affiliation: Department of Psychology, Stanford University, Stanford, California.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Norcia
authors.affiliation: CNRS, CRAN, UMR 7039, Vandœuvre-lès-Nancy, France.|Université de Lorraine, CRAN, UMR 7039, Vandœuvre-lès-Nancy, 54516, France.|Service de Neurologie, Centre Hospitalier Universitaire de Nancy, Nancy, 54000, France.
authors.forename: Louis G
authors.initials: LG
authors.lastname: Maillard
mesh_terms: D000293:Adolescent; D000328:Adult; D016880:Anisotropy; D001921:Brain / Q000473:pathology / Q000503:physiopathology*; D000069279:Drug Resistant Epilepsy / Q000473:pathology*; D017097:Electric Impedance; D004566:Electrodes; D004569:Electroencephalography; D005260:Female; D066128:Gray Matter / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology*; D066127:White Matter / Q000503:physiopathology; D055815:Young Adult
keywords: brain tissue; depth electrode; electric conductivity; epilepsy; human investigation; in-vivo measurement; stereoelectroencephalography; volume conduction