title: Impact of brain tissue filtering on neurostimulation fields: a modeling study.
abstract: Electrical neurostimulation techniques, such as deep brain stimulation (DBS) and transcranial magnetic stimulation (TMS), are increasingly used in the neurosciences, e.g., for studying brain function, and for neurotherapeutics, e.g., for treating depression, epilepsy, and Parkinson's disease. The characterization of electrical properties of brain tissue has guided our fundamental understanding and application of these methods, from electrophysiologic theory to clinical dosing-metrics. Nonetheless, prior computational models have primarily relied on ex-vivo impedance measurements. We recorded the in-vivo impedances of brain tissues during neurosurgical procedures and used these results to construct MRI guided computational models of TMS and DBS neurostimulatory fields and conductance-based models of neurons exposed to stimulation. We demonstrated that tissues carry neurostimulation currents through frequency dependent resistive and capacitive properties not typically accounted for by past neurostimulation modeling work. We show that these fundamental brain tissue properties can have significant effects on the neurostimulatory-fields (capacitive and resistive current composition and spatial/temporal dynamics) and neural responses (stimulation threshold, ionic currents, and membrane dynamics). These findings highlight the importance of tissue impedance properties on neurostimulation and impact our understanding of the biological mechanisms and technological potential of neurostimulatory methods.
authors.affiliation: Highland Instruments, Cambridge, MA, USA; Division of Health Sciences and Technology, Harvard Medical School/Massachusetts Institute of Technology, Boston, MA, USA. Electronic address: twagner@mit.edu.
authors.forename: Tim
authors.initials: T
authors.lastname: Wagner
authors.forename: Uri
authors.initials: U
authors.lastname: Eden
authors.forename: Jarrett
authors.initials: J
authors.lastname: Rushmore
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Russo
authors.forename: Laura
authors.initials: L
authors.lastname: Dipietro
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
authors.forename: Stephen
authors.initials: S
authors.lastname: Simon
authors.forename: Stephen
authors.initials: S
authors.lastname: Rotman
authors.forename: Naomi B
authors.initials: NB
authors.lastname: Pitskel
authors.forename: Ciro
authors.initials: C
authors.lastname: Ramos-Estebanez
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual-Leone
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Grodzinsky
authors.forename: Markus
authors.initials: M
authors.lastname: Zahn
authors.forename: Antoni
authors.initials: A
authors.lastname: Valero-Cabré
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D002415:Cats; D003198:Computer Simulation; D046690:Deep Brain Stimulation; D017097:Electric Impedance; D020342:Finite Element Analysis; D006801:Humans; D008959:Models, Neurological; D050781:Transcranial Magnetic Stimulation
keywords: CSF; Cellular models; Cerebral Spinal Fluid; DBS; Deep Brain Stimulation; FEM; Finite Element Model; HP; Hewlett Packard; IACUC; Institutional Animal Care and Use Committee; MRI; Magnetic Resonance Imaging; Neuromodulation; Neurostimulation; RMS; Root Mean Squared; TMS; Transcranial Magnetic Stimulation; VOA; Volumes of Activation